随着年龄的增加，记忆力的减退不可避免，现代生活节奏的加快，让失眠也成为多数人的常态。睡眠不足，会给大脑造成不可逆的损伤。比尔盖茨最近也开始说要早睡。
如果一切不可避免，或许给大脑足够的锻炼才是真正的解决之道。
每天AMC五道题，脑力活力没问题。
1. What is the value of
(A) 7 (B) 21 (C) 49 (D) 64 (E) 91
2. Menkara has a 4x6 index card. If she shortens the length of one side of this card by 1 inch, the card would have area 18 square inches. What would the area of the card be in square inches if instead she shortens the length of the other side by 1 inch?
(A) 16 (B) 17 (C) 18 (D) 19 (E) 20
3. What is the maximum number of balls of clay with radius 2 that can completely fit inside a cube of side length 6 assuming that the balls can be reshaped but not compressed before they are packed in the cube?
(A) 3 (B) 4 (C) 5 (D) 6 (E) 7
4. The six-digit number is prime for only one digit A. what is A？
(A) 1 (B) 3 (C) 5 (D) 7 (E) 9
5. Elmer the emu takes 44 equal strides to walk between consecutive telephone poles on a rural road. Oscar the ostrich can cover the same distance in 12 equal leaps. The telephone poles are evenly spaced, and the 41st pole along this road is exactly one mile (5280 feet) from the first pole. How much longer, in feet, is Oscar’s leap than Elmer’s stride?
(A) 6 (B) 8 (C) 10 (D) 11 (E) 15
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