zhouchuzc wrote:

Is the average (arithmetic mean) of w, x, y, and z less than 28?

(1) The average (arithmetic mean) of w, x, and y is less than 28.

(2) The average (arithmetic mean) of x, y, and z is less than 28.

Easy to fall for C trap..

Note - the numbers are not in any order...

Each statement alone is not enough as one variable is missing in each..

Combined..

average of w,x,y,x,y,z <28

So if we take w,x,y and z each less than 10, average will be <10..so <28...yes

Say w=70, y=7 and x=6 Avery<28

Also y=7,x=6 and z=70.. average<28

But X+y+w+z=70+7+6+70=153

So average=153/4=38...>28.. so Ans NO

Insufficient

E

_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372

2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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