Kazzen161 Report post Posted October 11, 2005 R had this Maths question for homework: Stella and Paolo each have three cards numbered 1,2 and 3. They each take one of the other person's cards. They then add together the numbers on the four cards left. What is the probability the total will be an odd number? He said but if they each take one of the other person's cards, they will still have three cards each! Looking at it, even the first sentence isn't that clear. Karen Quote Share this post Link to post Share on other sites
Tally Report post Posted October 11, 2005 Try re-wording the 2nd line to say, "they each take away one card and throw it away." Quote Share this post Link to post Share on other sites
Brook Report post Posted October 11, 2005 (edited) When it mentions 'other persons' cards, does that mean there is someone else too? Sorry, I'm a little confused also. Brook Tally I think you could be right. Edited October 11, 2005 by Brook Quote Share this post Link to post Share on other sites
Kathryn Report post Posted October 11, 2005 Nope. I agree with your son. It doesn't make sense to me either. Quote Share this post Link to post Share on other sites
Brook Report post Posted October 11, 2005 (edited) Mmmm, I think I get it now they actually take the others cards, but dont include them, they put them aside? Okay, it is getting late. Brook Dont know the answer though. Edited October 11, 2005 by Brook Quote Share this post Link to post Share on other sites
smallworld Report post Posted October 11, 2005 Karen, did your son use this ambiguity as an excuse not to do the homework ? My son would have, even if he could have got the right answer !! wac Quote Share this post Link to post Share on other sites
streamdreams Report post Posted October 12, 2005 R had this Maths question for homework: Stella and Paolo each have three cards numbered 1,2 and 3. They each take one of the other person's cards. They then add together the numbers on the four cards left. What is the probability the total will be an odd number? He said but if they each take one of the other person's cards, they will still have three cards each! Looking at it, even the first sentence isn't that clear. Karen He said but if they each take one of the other person's cards, they will still have three cards each! I think he is right but the english sucks as for the maths its straight forward; hint: to end up with an odd number for the total you must have an odd number of odd cards J Quote Share this post Link to post Share on other sites
phasmid Report post Posted October 12, 2005 Stella and Paolo each have three cards numbered 1,2 and 3. They each take one of the other person's cards. They then add together the numbers on the four cards left. What is the probability the total will be an odd number? What an awful question! It ought to read: Stella and Paolo each have three cards numbered; 1,2 and 3. They each take one of the other person's cards, and discard it. They then add together the numbers on the four cards left. What is the probability the total will be an odd number? Now that makes sense...even if I can't work out the answer Quote Share this post Link to post Share on other sites
call me jaded Report post Posted October 12, 2005 Yes it's badly worded. Do you want help to get the answer? I can explain how to do it if you need help. Quote Share this post Link to post Share on other sites
fiorelli Report post Posted October 12, 2005 have asked on another site I go on, and all are of the concensus that it is VERY badly worded! someone has put this though. don't know whether it will help bagpuss United Kingdom 25288 Posts Posted - 12 Oct 2005 : 13:13:56 -------------------------------------------------------------------------------- So, probability... Stella's cards in red, Paolo's in blue We start with 1, 2, 3, 1, 2, 3 and lose one of each, so we have 3x3=9 different possibilities 1, 2, 1, 2 Total = 6 1, 2, 1, 3 Total = 7 1, 2, 2, 3 Total = 8 1, 3, 1, 2 Total = 7 1, 3, 1, 3 Total = 8 1, 3, 2, 3 Total = 9 2, 3, 1, 2 Total = 8 2, 3, 1, 3 Total = 9 2, 3, 2, 3 Total = 10 Four of those are odd, so the chances are 4/9 that it will be odd. I'm sure there's a clever fancy way to work it out without working out the 9 possible scenarios (eg total = 12 before removal, probability of 2 being removed being odd = x, thus prob of remaining total being odd also equals x), but I always find doing it this way helps you understand better what is actually going on. Quote Share this post Link to post Share on other sites
fiorelli Report post Posted October 12, 2005 (edited) someone else on same site has put this... Knownowt United Kingdom 6294 Posts Posted - 12 Oct 2005 : 13:15:16 -------------------------------------------------------------------------------- I think the best way of approaching it is to look at the 2 cards each person is left with first. For them to add up to an odd number, you need either 1 or 3 to have been removed. So chances of each person's cards adding up to an odd number= 2/3 To have the total of all 4 being odd, you'd need one person's cards to have an odd total and the other to have an even total. Chance of S's cards being odd and P's being even= 2/3 x 1/3 = 2/9 plus chance of P's cards being odd and S's even = 2/3 x 1/3 = 2/9 So total chance = 4/9. Edited October 12, 2005 by fiorelli Quote Share this post Link to post Share on other sites
Canopus Report post Posted October 12, 2005 Bad wording makes maths questions harder. I always preferred questions that said things like "factorise this equation" rather than a commentary on some real world situation. Traditionally O Level maths questions were of the "factorise this equation" variety, but educational gurus decised in the mid 80s that maths was too boring, so went ahead and introduced all sorts of wordy drivel in the exam questions in the attempt to make things more appealing for the masses. This was a detrimental move for kids who find comprehension difficult but maths easy. They get the wrong answers because they misinterpret the question rather than get the maths wrong. When I did my A Level I opted for mechanics rather than statistics because the statistics questions were too wordy. Quote Share this post Link to post Share on other sites
Zemanski Report post Posted October 12, 2005 Karen, from a logical (AS) point of view your son's right - there are still 6 cards, not 4. Neither of them discarded/threw out/got rid of any cards. They 'take' them as in 'take into their posession'. But then who ever said maths was logical? When I took the test to become a fireman, there was a question like this. One of those classic 'Pumping water out of a pond as it fills, how long till it's empty' ones. But they didn't tell you how full the pond was to start with. So I answered by explaining what was wrong with the question. Didn't get the job, but later found out I got all the other questions right. Moral - it's better to be wrong than a smart alec. nemo Quote Share this post Link to post Share on other sites
Kazzen161 Report post Posted October 12, 2005 I did tell him to pretend they had thrown away the cards they took from each other. He was fine about doing the question afterwards, and had no problem working it out. Karen Quote Share this post Link to post Share on other sites
Kathryn Report post Posted October 13, 2005 (edited) It reminds me of the Paddington Bear story in which he is answering quiz questions on a TV show. He was asked something along the lines of: if it takes one man 20 minutes to fill a bath using to taps, how long will it take another man to fill the same bath using one tap? He answered "no time at all". His reasoning was that the first man hadn't let the water out. Edited October 13, 2005 by Kathryn Quote Share this post Link to post Share on other sites
jomica Report post Posted October 13, 2005 (edited) Edited this out. Had the wrong end of the stick entirely!!!! Jo Edited October 13, 2005 by jomica Quote Share this post Link to post Share on other sites
