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DS - assumption? When is it not enough? [#permalink]
14 Mar 2008, 00:37

00:00

A

B

C

D

E

Difficulty:

5% (low)

Question Stats:

0% (00:00) correct
0% (00:00) wrong based on 0 sessions

Hi, DS - for those questions that final answers are E, they lack of info. But i wanna hear from u guys the exp

********** This is a very simple one

A piece of wood 7 feet long is cut into three pieces. What is the length of each of the pieces? (1) The length of the longest piece is equal to the sum of the lengths of the other two pieces. (2) The length of the shortest piece is 6 inches.

Need to solve it, could take less than 45s. However what i did wrongly was that i think how they cut this piece? So i chose E instead of C

While some like this is so clear: How many chocolate bars 2 inches wide and 4 inches long can be packed into carton Q ? (1) The inside dimensions of carton Q are 8 inches by 8 inches by 12 inches. (2) The width of carton Q is equal to the height and 5/4 of the length. -> E

Just afraid that i 'll jump to same pitfall again, appreciate if anyone got some 'guideline'. Thanks!!

Re: DS - assumption? When is it not enough? [#permalink]
14 Mar 2008, 07:22

You need a systematic approach to solve this problem. Moreover do not assume anything from your side. What is stated in question is only true, things that are not stated should not be assumed. Also try to reword the problem so that you can understand it better.

Like if you are given a integer. Do not rule out -ve, +ve, as well as 0.

Moreover go to each statement one by one and see if you can put them up in a mathematical form or not. If you can then that will help you in combining both the statements.

E.g. take the wood log case. Question says that 7 feet wood is cut into three pieces, say their lengths are x,y,z. So as per question x+y+z=7

Statement 1: tells you x+y=z(assuming that z is the longest piece) substituting it in original equation we have 2z=7 => z=3.5 feet we have length of longest piece but length of other 2 pieces although 3.5 can be any thing like 1.5, 2 or 1, 2.5. so length of all 3 pieces cannot be determined by this statement alone.

Statement 2: Tells us that smallest piece is 0.5 feet. but does not tells us about length of other 2 pieces, so this is insufficient.

Combining 1 and 2: From 1 we have longest piece = 3.5 feet, & x+y=3.5. From 2 we know x=0.5(assuming x is the smallest piece) =>y=3.5-0.5=3 feet We have length of all the pieces. So together both can answer the question.

Re: DS - assumption? When is it not enough? [#permalink]
14 Mar 2008, 13:43

thanks for the explanation, i know if it is the case i can find out. The thing is somehow i thought the way the wood is cut affects the result, since i don't know the shape, and how it is cut, i choose E (because i shouldnt make any assumption)... ... so it crossed my mind to ask when can u assume such kind of thing?..maybe get crazy after solving some prob =)) Anyway thks!

gmatclubot

Re: DS - assumption? When is it not enough?
[#permalink]
14 Mar 2008, 13:43