Brain teaser
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If two typists can type two pages in two minutes, how many typists will it take to type 18 pages in six minutes?
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If it were two hours later, it would be half as long until midnight as it would be if it were an hour later. What time is it now?
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What is the number that is one half of one quarter of one tenth of 400?
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If you count from 1 to 100, how many 7's will you pass on the way?
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Two men, starting at the same point, walk in opposite directions for 4 meters, turn left and walk another 3 meters. What is the distance between them?
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If a circle is one, how many is an octagon?
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There are 1200 elephants in a herd. Some have pink and green stripes, some are all pink and some are all blue. One third are pure pink. Is it true that 400 elephants are definitely blue?
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Which word of four letters can be added to the front of the following words to create other English words?
CARD BOX CODE BAG HASTE
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Following the pattern shown in the number sequence below, what is the missing number?
1 8 27 ? 125 216 -
Four years ago, Jane was twice as old as Sam. Four years on from now, Sam will be 3/4 of Jane's age. How old is Jane now?
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Which number comes next in this series of numbers?
2 3 5 7 11 13 ? -
Which letter comes next in this series of letters?
B A C B D C E D F ?
six
9 pm
5
20
10 metres
eight
Can't say.
64
12
17
E
EDIT: 4 and 12.
Answer to all questions is 3.50
number 4 is 20 cuz u have to count the 70's
Ah of course, I only counted the 70.....
1) 6 if 2 typists can do 2 pages in 2 minutes, they can do 6 in 6 minutes. 3 times the number of typists.
2) 9pm
3) 5
4) 20
5)
6) 10, a 3 4 5 pythag triple
7) 8
8) No, proof by contradiction - 400 are pink, some are pink and green some are blue. 399 blue and rest pink and green.
9) post
10) 64 - cubes
11) 12 - had to get the paper out for this one
12) 17, primes
13) E G F, required pen and paper too. convert letters into numbers and it pops out pretty quickly.
Number twelve should be 17. It's a list of prime numbers. Right? 15 isn't prime.
Yeah spot on - 17 is correct.
On 13, you can pair them like this: (2, 1); (3, 2); (4, 3); (5, 4), (6, 5); (7, 6); (8, 7)... You already see what's going on, thus the answer is 5, i.e. E.
Or your can Alternate letters increase by one
I don't get number 7, it's 8 because an octagon has 8 sides?
Circle has one line, octagon has eight
1 7 2 17 3 27 4 37 5 47 6 57 7 67 8 77 9 87 10 97 11 70 12 71 13 72 14 73 15 74 16 75 17 76 18 78 19 79
where did you get the 20 from in q 4? 20
77 has 2 of them...
77
7-7
two
Probably counted 77 twice.
: O lol, 20 it is.
Wouldn't the anwer to number one be three? Not six?
If you have six typists, and each typist can do one page per minute, that means in three minutes you will have 18 pages.
Basicly the equation should look like this: [(1 page/min)/1 typist] = [(3 pages/min)/x typists]
I can see why you'd think that based on the wording, but the way you have to look at is: each typist can type 1 page in 2 minutes, not, each can do a page per minute. So, yes, 6 is correct.
I wish my brain teaser was this easy back in the day. You should see some of the ones at places like DE Shaw.
don't need as many smart people in IBD vs. people who can get work done
Wouldn't the anwer to number one be three? Not six?
If you have six typists, and each typist can do one page per minute, that means in three minutes you will have 18 pages.
Basicly the equation should look like this: [(1 page/min)/1 typist] = [(3 pages/min)/x typists]
If 2 typists can type 2 pages in 2 minutes, they can type 6 pages in 6 minutes. Therefore if you have 6 (=2 x 3) typists, you get 18 (=6 x 3) pages in the same 6 minutes... Does that make sense?
Each typist is producing 0.5 pages each minute. With 6 people typing:
End of Min 1 = 3 pages total End of Min 2 = 6 pages total End of Min 3 = 9 pages total End of Min 4 = 12 pages total End of Min 5 = 15 pages total End of Min 6 = 18 pages total
The sad thing is at some shops people will get dinged for fucking up a brain teaser. You see this more in trading I think. Anyway they're a shitty way to evaluate someone in an interview.
I agree, but in terms of raw mathematical ability if you're getting any of the above braintreasers wrong that's a pretty bad sign, though not necessarily autoding.
on the other hand, I've also seen some really obscure S&T-oriented brainteasers (set theory wtf). There was one I read on here about dropping balls off a 100-story building that I definitely wouldn't have solved during the interview's allotted time.
I'm sorry, but those brainteasers are ridiculously easy. If they can't handle those under pressure in an interview setting, what happens when they're on the trading floor getting squeezed? I agree that the more ridiculous brainteasers are unnecessary, but these simple ones can definitely tell you a lot about a person.
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