Re: [問題]來欣數學Q部分
※ 引述《voices (總是昏睡中~)》之銘言：
: Q2
: 20. The "reflection" of a positive integer is obtained by reversing its digits.
: For example, 321 is the reflection of 123. The difference between a
: five-digit integer and its reflection must be divisible by which of the
: following?
: A.2 B.4 C.5 D.6 E.9 Ans:E
假設是 abcde-edcba 其中a,b,c,d,e為0~9的正整數
abcde=10000a+1000b+100c+10d+e edcba=10000e+1000d+100c+10b+a
abcde-edcba=9999a+990b-990d-9999e=9[1111*(a-e)+110*(b-d)]
所以一定能被9整除
: Q21
: 21. The scale drawing of a certain room is a rectangle 5 inches by 6 inches. If
: the drawing has the scale 1/4 inch to 1 foot, which of the following will
: give the actual number of square feet of the room?
: A.15/8 B.15/2 C.90 D.120 E.480 Ans:E
題目是說用縮小比例的圖畫房間,圖畫出來是邊長5 inches和6 inches的長方體
已知比例尺是1/4 inch對上1 foot,請問這個房間的實際面積?
5 inches => 20 feet 6 inches => 24 feet
所以實際面積就是 20*24=480 square feet
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※ 編輯: tingting88 來自: 140.112.4.249 (06/04 10:02)
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