stats

[ricaototti]

If set S = {7, y, 12, 8, x, 9}, is x + y less than 18?

(1) The range of set S is less than 9.

(2) The average of x and y is less than the average of set S.

OA b

But I dont get the reasoning. I would like to have a step by step explanation of why B is correct.

What I did for B: I just plugged in a few numbers.That is what I usually do when I dont have a quick nice approach to tackle the question. Should I change this strategy? It doesnt always work out all right...

How many questions on Stats in the real GMAT? By stats I mean what includes mean, range, std, median....

THANKS

[parallel_chase]

If set S = {7, y, 12, 8, x, 9}, is x + y less than 18?

(1) The range of set S is less than 9.

(2) The average of x and y is less than the average of set S.

OA b


But I dont get the reasoning. I would like to have a step by step explanation of why B is correct.

What I did for B: I just plugged in a few numbers.That is what I usually do when I dont have a quick nice approach to tackle the question. Should I change this strategy? It doesnt always work out all right...

How many questions on Stats in the real GMAT? By stats I mean what includes mean, range, std, median....

THANKS

Statement I

range of the set is less than 9, x could be anything and y could be anything.

x+y can be less than 18, x+y can be more than 18.

Insufficient.

Statement II

(x+y)/2 < (36+x+y)/6

(x+y)/2 < 6 + (x+y)/6

x+y < 12 + (x+y)/3

If you insert values for x and y, you will notice that x+y will always be less than 18 to satisfy the above equation.

Answer is no.
Hence Sufficient.

Answer is B.

You can see anywhere between 2-3 questions on stats, but it could be more or it could be less on the actual GMAT.

Hope this helps.

[mayur00]

I think ricaototti's solutions is correct.

However, you can further simplify
(x+y)/2 < (36+x+y)/6

to give x+y<18