Data Sufficiency

Akansha wrote:If x is a positive number less than 10, is z greater than average of x and 10?
a. z is closer to 10 than x on the number line
b. z = 5x

OA is A

Question is: If x < 10, then is z > (x + 10)/2)?

(1) z is closer to 10 than x on the number line implies that distance between z and 10 is less than the distance between z and x (see the number line below).


So, z is more closer to 10 implies that average of x and 10 will be less than z.
So, z > (x + 10)/2) holds true.
So, (1) is SUFFICIENT.

(2) z = 5x does not give us the required info to decide whether z > (x + 10)/2) or not.
So, (2) is NOT SUFFICIENT.

The correct answer is A.