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Math tips on when to stop looking for a better partner!

April 23, 2009

The book how long is a piece of string by Rob. Eastaway and Jeremy Wyndaham makes interesting and amusing reading. It is what it says it is: The hidden mathematics of everyday life.

I found it fun to read. Let me give an example from the book. There is this chapter on how to maximise your chances of ending up with the most suitable partner. Selecting the best partner can be tricky as one does not meet all potential partners at the same time. Even in an arranged marriage system it is not always possible to keep one side waiting because they will be seeing other people and delaying tactics could mean losing out. But a decision has to be made even though there is no way of finding out who or what is coming next. The authors have compared this decision (of selecting a partner) to other decisions like finding the right apartment or the right job. Each of these choices come to us one by one. If an offer is rejected there is often no way of going back. So when does one stop looking? The way this book explains it might sound a little cold-blooded but it’s amusing all the same. And well, many people do keep waiting until they find the “best.”

The authors give an example of a man. Let’s call him Rajesh. Rajesh has ten girls lined up. He knows that he is a good guy, reasonably good looking and with a good job. He knows that at least a couple of these girls will say yes to him. But who should he say yes to? Suppose he says yes too early he could lose out if someone better comes along!

Let’s say he meets the first girl, Reena. He finds her okay but the chances of her being the most suitable of the 10 are just 1 in 10. But if he says Yes to the first girl who is “better” than Reena, perhaps the second one he meets, then he increases his chances (of ending up with the best amongst the 10) from 1 in 10 to 1 in 5.

Rajesh can always keep rejecting girl after girl, hoping that the next one will be “better” than the previous but there are strong chances that somewhere along the line he might say no to someone who is the most suitable of them all. So this is a risky strategy. The “better” person may have already come and gone! Ofcourse, there is a chance that the last one is the best but that’s a slim chance, only 1 in 10.

So what the authors are saying is that if someone has the possibility of meeting 10 potential partners then they can  improve their chances of getting the best if they choose the best of the first three they meet. This way, mathematically, there is the highest chance of them ending up with the “best” partner. The authors admit that there are flaws in this plan because there is no way of knowing exactly how many potential partners you will meet in your life, but according to their calculations a person should settle down after meeting about 37% of  the potential partners. If this is not done, then the likelihood that the “best” partner has passed by keeps increasing. Finally you reach an age beyond which you have told yourself that you cannot wait (for marriage) and you have no choice but to choose the last one.

The authors have demonstrated that this works by experimenting with a blind date game!

Another interesting chapter in this book is on how conmen get rich. Simple mathematics is used to fool people. The authors give an example of a football scam. I’ve changed the example to cricket.

The conmen send an email to Mr. Kumar and tell him that the Rajasthan Royals are going to beat the Mumbai Indians that day at the IPL and ask him if he would like to subscribe to their predictions for all the IPL matches. Mr. Kumar is skeptical and deletes the mail, congratulating himself on how he has managed to see through this scam. But well, the Rajasthan Royals does win and then Kumar gets another mail, this time predicting the win of the Delhi Daredevils against the Kolkata KnightRiders. When this comes true Mr. Kumar tells his friends about this, but even then he does not subscribe. After all, this could be sheer luck. But the emails continue, and each time the prediction turns out to be correct. All in all five emails are sent and Mr. Kumar is finally sucked in. He subscribes by paying a designated amount.

Everyone who has received these correct predictions may not subscribe but even if one in a hundred does the scamsters have made money.

The way it’s done is simple. Thousands of similar emails are sent out, half of them predict a victory for one team, and the other half victory for the other team. Then the next email goes out to only those who had got the correct prediction….and so it continues until at least about a hundred people have received correct email predictions at least five times. Out of these hundred the chances are that a couple of people will pay the amount and subscribe!

The book has some other interesting workings, like that of a taxi meter and it explains why weather forecasters are often wrong, and the patterns behind a hit single. All in all 16 chapters, each dealing with something different. A good book to browse through!

(Photo is by me and copyrighted)

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49 Comments leave one →
  1. locutus83 permalink
    April 23, 2009 4:03 pm

    Very very interesting! This is something very much up my street. I love to read how probability theory and other mathematical theories are so deeply enmeshed in our daily lives.
    Probability theory can help a lot while we are making choices. Sometimes the order of choice influences the probability, which is demonstrated by the “choosing the best mate” problem.
    Apparently many top Poker players have successfully used card-suit and card order-based probability to bluff “mathematically” and win many times.

    If you and anybody else like reading such interesting non-fiction, may I also recommend a classic book How to Cut a Cake: And other Mathematical Conondrums by Ian Stewart, and another classic Tipping Point : How Little Things Can make a big difference by Malcolm Gladwell.

    There was an old Russian Mir Publishers book called “Mathematics for Fun” which was a very good read, but I can’t remember the author’s name.

  2. April 23, 2009 4:03 pm

    Interesting stuff…
    Never knew that even decisions attributed to heart can also be a function of some mathematical formulae.
    But I must say what was said in BEAUTIFUL MIND about going after the blond logic.
    It was really awesome the way he gave that logic.
    Wow…love knows maths (actually) 😉

  3. April 23, 2009 5:01 pm

    I believe that the calculations have already been done (Like marriages being fixed in heaven!). I would rather suggest people not to wait for three choices even – just take the first one! It just doesn’t make a difference, yaar 😉

    Destination Infinity

  4. April 23, 2009 5:42 pm

    Adding it to my ‘must read’ list. Thanks a lot. This is very interesting! Was reminded of Freakonomics after reading your review…

  5. April 23, 2009 6:52 pm

    hey looks to be a very interesting book, totally my kind :)..surely will try to get hold of this one

  6. Dev permalink
    April 23, 2009 9:04 pm

    Nita, that was cool! I knew somewhere that there has to be a book about this. I have no doubt in my mind that Probability theory has lot of applications in our lives, including dating. I once tried to convince my friend, who is not evry social and quite shy with girls, that simple mathematics prove that he has to to meet as many people as possible to find that ideal girl for him. For instance, any girl he comes across has not more than 1/4 possibility of being single/available. Going further, out of those available single girls, possibility of him liking her is not more than 1/5..and even further, once he finds her suitable for dating, probability of her finding him suitable is another 1/5..
    So, chances of him being hitched with any girl he meets is not more than 1/4*1/5*1/5 = 1/100 !!!!
    So, he should try to meet atleast 100 girls before he could hope for even dating..
    Voila..I should also write a book now!!

    P.S. Nita, on a different note, I hope you were not serious in congratulating me on my blog. Either you didnt read the whole post (and saw the pic) or you were pulling my leg. 🙂

    Dev, not only did I read the whole post but also saw the old lady’s pic! I was rather confused but then I thought it was because you were being bashful or something. I was seriously confused! So I thought I would be on the safe side and congratulated you! 🙂 – Nita.
    p.s. The probablities you mention are interesting! I think the more attractive the person is, and the smarter and richer, the probablities go up as there are fewer chances of rejection. 🙂

  7. April 23, 2009 10:00 pm

    sounds interesting 🙂

  8. April 23, 2009 10:06 pm

    Cheating people through email is very common these days. I guess everyone would be getting the msn-yahoo online lottery winner email. 😀

  9. Dev permalink
    April 23, 2009 10:12 pm

    Nita, :). I described that woman exactly as she were in the picture..if you read the text around that pic, you will see .
    Actually got that pic as a forward from a friend and I immediately spun a post around it. 🙂

    Regarding my probability theory, you are right. Probabilities can go up or down depending on other factors. My numbers are supposed to be for an average joe..

  10. openlight permalink
    April 23, 2009 11:02 pm

    Interesting, maths and love is good combination now.

    I think that finding a suitable girl is not probabilistic but linked to MaxMin, every human has an list of characteristics (looks, intellect,education,etc.) and is also has an upper and an lower bound to it.

    Max is 100% approval at any time, min is the least one can accept and then there is level of contentment. I feel that when one finds a mate at contentment level, one should stop.

    Rest, the loose / win email was good to read.

  11. rags permalink
    April 23, 2009 11:10 pm

    Interesting post! But what if you meet the ‘ideal person’ after marriage 😉

    Honestly all this talk about meeting the ‘ideal’ and ‘right’ person…. Don’t people change over time… There are no ideal people only ideal dreams..

  12. April 23, 2009 11:36 pm

    Sounds pretty interesting, especially since am going through the marital process now. 😀

  13. April 24, 2009 12:31 am


    You say to Dev: “I think the more attractive the person is, and the smarter and richer, the probablities go up as there are fewer chances of rejection.”

    I think this is more true of men than of women. Worldwide. Particularly when the woman is smarter and/ or richer.

    Re the book’s thesis, I think the maths is never hidden. It is right there. In front of us. But people do not necessarily base their decisions on logic and data. Which is just as well. For there is something to be said about the stereotypical geek who does so much maths, that the girl just leaves.

    And of course, as Robbie Williams sang: “..all the best women are married, all the handsome men are gay, feel deprived…” 😉

    • April 24, 2009 7:14 am

      Ah, Shefaly, that was the exact same song that came to my mind when I read this post, because I had long discussions in university days (very mathematical) around it. Unfortunately I don’t remember the derivation now, but the conclusion was that after some generations he’d sing all gay men are handsome (instead of all handsome men are gay) which, as you know, is true…. lol 😉 I called it the ‘law of enrichment’ and damn, I dont remember the derivation 😦

  14. April 24, 2009 1:09 am

    Like @shefaly mentioned, Mathematics is everywhere.
    Thanks for the post.
    May be of interest to you: Mathematics and Sports


  15. April 24, 2009 7:16 am

    Nita, very entertaining post. 🙂 I am sure, all of us who actively dated know in some way or the other about the exponential decay curve of finding a partner.

    • Vivek Khadpekar permalink
      April 24, 2009 8:09 am


      “Exponential decay curve!” I like that. But as you would know, an change from 100 to 200 counts as a 100 per cent increase, whereas one from 200 to 100 counts as only 50 per cent decrease. So the flame may go out, but the embers never die. 🙂

  16. April 24, 2009 7:58 am

    locutus83, thanks for the references! 🙂

    Dev, Mahendra, Rambler, Xylene, Vishesh, Nikhil and Priyank, thanks!

    DI and openlight, I am inclined to agree with you, go for the first one you like or are content with! After all we ain’t shopping! 🙂

    rags, true partners often change together! 🙂

    Jo, best of luck! 🙂 But go easy!

    Shefaly, I guess for women it’s different criteria. A stunningly beautiful woman could probably have whom she wants!

    • April 24, 2009 2:19 pm


      When I read “I think the more attractive the person is, and the smarter and richer, the probablities go up as there are fewer chances of rejection.”, I take it to mean the rejection _of_ the said attractive person, not rejection _by_ the said attractive person.


      Smart/ rich woman may find few takers/ faces more rejection (because she feels a majority of suitors inferior);

      Pretty woman finds many takers/ doles out more rejection (purely a game of probabilities especially if the queue is long).

      Just parsin’ 🙂

      • rags permalink
        April 24, 2009 9:58 pm

        “Smart/ rich woman may find few takers/ faces more rejection (because she feels a majority of suitors inferior”

        But its the woman who does the rejection here right? So how could she be the one facing rejection?

        • April 24, 2009 10:10 pm

          I can see what boo boo I committed.

          I wanted to say “because she makes a majority of suitors feel inferior” but clearly a Freudian slip happened there. No comments on that slip 😉

          Perhaps with that corrigendum, my point is clearer?

          Smart women are often courted avidly, usually when they are in educational institutions and provide delightful companionship, sometimes also when in professional settings when they seem exciting and may make boring work settings intellectually scintillating. But many are often dumped unceremoniously for the same qualities – and the fact that they do not need men to provide for anything.

          Of course, exceptionally I do not cite any stats but I would offer this as a working hypothesis which we can verify or reject using additional empirical data.

          • rags permalink
            April 25, 2009 11:53 am

            Freudian slip, eh? 😉

            But being the die hard optimist that I am I won’t agree with that even if it is only a hypothesis. 🙂

            Smart companions at work make smart companions for life.

            • April 25, 2009 12:34 pm

              No doubt they do but only a few men are smart enough not to let their egos interfere with their assessment of long-term potential of a relationship 🙂

              • rags permalink
                April 25, 2009 10:49 pm

                Honestly, why put up with men who don’t even have that basic common sense? Its better to wait for someone who’s actually worth the trouble. 🙂

                • April 26, 2009 12:45 am

                  Frogs and prince come to mind. 🙂

                  • Vivek Khadpekar permalink
                    April 26, 2009 5:21 am


                    I wonder if you mean the original story or this take on it by a friend of mine: “You have to kiss many frogs before you find your prince charming.”

  17. April 24, 2009 9:33 am

    How about a walk in interview and declaring results at the end of the day?

    • Vivek Khadpekar permalink
      April 24, 2009 11:18 am

      Shrinidhi Hande,

      Our ancients had and even quicker method: it was called swayamvara. In theory, the woman had the last word, but of course who could compete for her hand was carefully regulated. Despite all the precautions there were occasional goof-ups, as in the case of Draupadi (buy one, get four free!), but these happened after the results were out — and the results were instant; you did not even have to wait until the end of the day.

  18. April 24, 2009 9:48 am

    GOD! Why am i sooooooo Dumb at mathemetics!! Why, why, why!!!

    😀 😀 this was an interesting read nonetheless! 🙂

  19. ruSh.Me permalink
    April 24, 2009 11:47 am

    Best of first 3… 😦
    Give the other 7 a chance too… 🙂

    As of facts here are some more..!!

    Just about 3 people are born every second, and about 1.3333 people die every second. The result is about a 2 and 2/3 net increase of people every second. Almost 10 people more live on this Earth now, than before you finished reading this. 😀

    And how could you not know about Raakhi ka Swayambar!!

  20. April 24, 2009 10:10 pm


    An interesting read not so much on the maths but the psychology of how the maths can be distorted:

    • April 27, 2009 7:34 pm

      Shefaly, thank for an interesting link! It is sad, but true…

  21. April 25, 2009 12:26 pm

    @ Nita : Did the book by any chance mention what are the chances that the bread dough you are working on won’t rise?

  22. April 25, 2009 2:45 pm

    Very interesting Nita and great timing. 😉

  23. April 26, 2009 2:29 am

    I think that GOD really gives you the sign that this boy/girl is the right one .. At least in my case .. When I saw her first time in the class, I was like this girl has something .. THen we became friends, good friends, close friends, very close friends, boyfriend-girlfrend and now she is my lovely wife ..

    Even though we were from different religions(Jain-Hindu), different nature(she was topper in engineering-very studious .. I was happy-go-lucky kind but intelligent) – still we were attracted and we tried to spend a good time ..

    It’s all coz of God’s grace .. Everything was smooth .. and yeah, GOd did give me the signals that she is THE ONE !!

    • Vivek Khadpekar permalink
      April 26, 2009 5:24 am


      I am eternally awestrcuk by people who have a hotline to god.

  24. rags permalink
    April 27, 2009 12:21 am

    You’re not the only one Vivek. I’m jealous of people who seem to have ‘higher connections’!

  25. Vivek Khadpekar permalink
    April 27, 2009 8:41 am


    There’s a vast difference between being ‘jealous’ and being ‘awestruck’. Also, the latter could be construed as a euphemism 😉

  26. rags permalink
    April 27, 2009 10:02 am

    Ok, got it. 🙂 Yep, I’m jealous alright … I wish I had divine revelations on stuff.

  27. April 27, 2009 10:20 am

    Sakhi, so was your partner the best of three? 🙂

    ruSh.Me, I think Raakhee has finally lost it! I mean seriously, the chances of her getting some gold digger are very high the way she is going to about it. I do have faith in the arranged marriage system, but only if the person is from a known network.Anything outside that increases the risk of disaster!

    Odzer, you will be surprised at the kind of stuff the book has! Even weird things as to why Monday comes round so quickly! 🙂

    Amit, all the best to you! 🙂

    Soham, I think the God you refer to is yourself. 🙂 🙂 But seriously, it’s good to have faith. You are a lucky guy.

    Shefaly, interesting link! I love anything to do with false perceptions and the real thing. Thanks.

    • April 27, 2009 7:38 pm

      Nita, a funny book indeed 🙂
      I don’t know if maths can be really applied to such things as marriage, I blieve the choice of a partner is much more …sacred.
      Although there is lots of confusion nowadays about it, somehow people are still manage to find their “half” – not all but some still do!

      • rags permalink
        April 27, 2009 10:31 pm

        I agree! Surveys and stats be damned!

  28. April 27, 2009 1:18 pm

    lovely post nita…should read this book soon…. 🙂

  29. Vivek Khadpekar permalink
    April 27, 2009 3:50 pm

    Forget the maths, forget the stats, forget Levine and Marano (Shefaly’s link). Beauty lies in the eyes of the beer-holder.

    If you don’t believe me, go to

  30. April 27, 2009 4:49 pm

    Those, who keep up with research, know better. The beer-goggle effect is a myth, albeit one widely believed:

    • Vivek Khadpekar permalink
      April 27, 2009 5:35 pm


      Speaking for myself, if I find a woman attractive her age (real or imagined) does not matter; and it has been that way since I was in my late teens (whether UI or not). I cited that one because I found it humorous. My tenet in real life is the one from which it is derived 🙂

  31. May 8, 2009 11:37 pm

    An interesting book indeed!!

  32. sourabh permalink
    December 21, 2009 6:52 pm

    Yes,but mathematical model will fail if u take into account the other condition like ‘Patrika Matching ‘ & Manglik ….Is their any rule for that too ?

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