Barry has three sisters. The average age of the three sisters is 27 . The average age of Barry and his three sisters is 28 . What is Barry's age?
(A) 1
(B) 30
(C) 4
(D) 29
(E) 31

Part B: Each correct answer is worth 6.
Since the average age of the three sisters is 27 , then the sum of their ages is $3 \times 27=81$.

When Barry is included the average age of the four people is 28 , so the sum of the ages of the four people is $4 \times 28=112$.

Barry's age is the difference between the sum of the ages of all four people and the sum of the ages of the three sisters, which equals $112-81$ or 31 .

ANSWER: (E)