Bunuel
What is the average (arithmetic mean) of x and y?
(1) The average of x and 2y is 10.
(2) The average of 2x and 7y is 32.
Solution:
Question Stem Analysis:We need to determine the average of x and y, i.e., the value of (x + y)/2. Notice that if we can determine the values of x and y, then we can determine the value of (x + y)/2.
Statement One Alone:We are given that (x + 2y)/2 = 10. However, since we can’t determine either the value of x or of y, we can’t determine the value of (x + y)/2. Statement one alone is not sufficient.
Statement Two Alone:We are given that (2x + 7y)/2 = 32. However, since we can’t determine either the value of x or of y, we can’t determine the value of (x + y)/2. Statement two alone is not sufficient.
Statements One and Two Together:From the two statements, we have two linear equations in two variables. Note that neither equation is dependent on the other, which means that one equation is not a linear multiple of the other. Thus, we can solve for the values of x and y, and hence we can determine the value of (x + y)/2. Both statements are sufficient.
Answer: C