Bunuel
Q is the set of all integers between A and B, inclusive. The average (arithmetic mean) of Q is m. If A<B, and B=190, what is the value of A?
(1) Q contains 40 terms that are greater than m.
(2) m=150
Project DS Butler Data Sufficiency (DS3)
For DS butler Questions Click Here Q is the set of all integers between A and B, inclusive. The average (arithmetic mean) of Q is m. If A<B, and B=190, what is the value of A?First of all, in order the answer to be B, it should be mentioned that A is an integer itself. Suppose we are told that.
So, we are told that
the average of integers between integer A and 190 is m. Notice that Q is a set of consecutive integers, thus its average, m, equals to the median.
(1) Q contains 40 terms that are greater than m.
If A is odd, then the number of integers between odd A and 190 would be even, so in this case m would be the average of two middle terms, so not an integer. Thus, in this case we would have that there are 80 integers in the set, 40 less than m and 40 greater than m. This gives the value of A as 111.
If A is eve, then the number of integers between even A and 190 would be odd, so in this case m would be the middle terms, so an integer. Thus, in this case we would have that there are 81 integers in the set, 40 less than m,
m itself and 40 greater than m. This gives the value of A as 110.
(2) m=150 --> m = (A + B)/2 --> 150 = (A + 190)/2 --> A = 110. Sufficient.
Answer: B.
Hope it's clear.