BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

geometry data sufficiency

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 71
Joined: Tue Mar 03, 2009 1:24 pm

geometry data sufficiency

by coolgirl26 » Sun Apr 19, 2009 12:26 pm
What is perimeter of rectangle having area of 60

L* W= 60


1) length and width of rectangle are even integers smaller than 25

2) length of rectangle is larger than 3 times the width

answer is A


But how

pleas gtive me some knowledge about the perimeter etc. and short cuts to solve this problem

thank u for ur help
Top
Source: — Data Sufficiency |
User avatar
Site Admin
Posts: 2567
Joined: Thu Jan 01, 2009 10:05 am
Thanked: 712 times
Followed by:550 members
GMAT Score:770

by DanaJ » Sun Apr 19, 2009 12:49 pm
You are right to start with L*W = 60. Now, think about L and W for a second: they're lengths of sides, so they must be positive. With that in mind we can go on to analyze the stmts:

1. the key word here is "integers": there are plenty of numbers that, when multiplied, yield 60. For instance, 2/3 and 90 and a lot of other fractions. But there are only a few integers that follow this rule and even fewer even integers that are smaller than 25.
In order to zoom in on these particular integers, just use the prime factorization of 60 = 2^2*3*5.
Now, we know we're dealing with even integers, so both L and W get a 2 respectively. Now, after splitting the 2s, you need to figure out what you're going to do with 3 and 5. Say you choose to have L = 2*3*5 (meaning you put both 3 and 5 in the same place) and W = 2. But this means that L = 30, which is greater than 25. This is why you need to have L = 2*3 and W = 2*5 or L = 2*5 and W = 2*3.

In any case, you have that L + w = 6 + 10 = 16. Since the perimeter is 2(L + W), it will be 32. So 1 is sufficient.

2. L > 3W doesn't help much. Consider some cases:
a. L = 60 and W = 1
b. L = 90 and W = 2/3.
Since there is no single solution, 2 is insufficient.
Top
Post new topic Post Reply
• Page 1 of 1