[問題]OG(11th)DS-Q38

[neverinmind]

|___(a book rack)___|

|________x________|


38.Will the first 10 volumes of a 20-volume encyclopedia fit upright in the book rack shown above?

(1)x=50
(2)Twelve of the volumes have an average (arithmetic mean) thickness of 5 centimeters.

Answer: (E)

為什麼不充分呢？是說前提沒有假設每本書的厚度都一樣嗎？

Many thanks.

[FrankChang]

(2)是指前12本的"平均"為5cm,所以每本書厚度未必相同
前12本總和60cm長不保證前10本總和小於等於50.