gmatophobia
PS Question 1 - May 27 If the least common multiple of 2x and y is 400 and the greatest common divisor of 6x and 3y is 30, what is the value of (x*y)/2 A. 100 B. 500 C. 1000 D. 1500 E. 2000 Source:
GMATWhiz | Difficulty: Hard
I am out of practice, but let me try this:
LCM(2x,y) is 400.
GCF(6x, 3y)=30
recall that
xy=LCM(x,y)*GCF(x,y)
Now, we don’t have xy so this is unusable.
What we can do, is this:
LCM(6x,3y)=3*400=1200.
So we have that
18xy=1200*30=36000
xy=2000
xy/2=1000
C
gmatophobia
DS Question 1 - May 27 A set of integers, S, contains more than one element. Is the range of S greater than its mean? (1) S does not contain positive integers. (2) The mean of S is negative. Source: 800 Score | Difficulty: Hard
1) Consider the case where S is just composed of 0. The range and the mean are exactly the same. However, if you consider the case where S is composed of negatives, or 0 with some distinct negatives, the range must be higher than the mean. INS.
2) The mean of S is negative.
Consider the following cases:
the max of S is a positive number, and the min of x is some negative number. In this case, range is greater than mean.
the max of s is 0, and the min of x is some negative number. Range>mean.
the max of s is the mean, and the min of x is the mean (both negative numbers). range>mean (0>negative numbers)
B should be suff.
gmatophobia
DS Question 1 - May 27 A set of integers, S, contains more than one element. Is the range of S greater than its mean? (1) S does not contain positive integers. (2) The mean of S is negative. Source: 800 Score | Difficulty: Hard
Very nice question.. Enjoyed it