AMC8 2009

AMC8 2009 · Q1

AMC8 2009 · Q1. It mainly tests Sequences & recursion (algebra), Fractions.

Bridget bought a bag of apples at the grocery store. She gave half of the apples to Ann. Then she gave Cassie 3 apples, keeping 4 apples for herself. How many apples did Bridget buy?

Bridget在杂货店买了一袋苹果。她把苹果的一半给了Ann。然后她给了Cassie 3个苹果，自己留了4个苹果。Bridget一共买了多少个苹果？

(A) 3 3

(B) 4 4

(D) 11 11

(E) 14 14

Answer

Correct choice: (E)

正确答案：（E）

Solution

Work backwards. Bridget had 7 apples before she gave Cassie 3 apples. These 7 apples were half of Bridget's 14 original apples. Let $B$ be the original number of apples. $\frac{B}{2} - 3 = 4$ $\frac{B}{2} = 7$ $B = 14$.

逆向工作。Bridget在给Cassie 3个苹果之前有7个苹果。这7个苹果是Bridget原来14个苹果的一半。设$B$为原来苹果的数量。 $\frac{B}{2} - 3 = 4$ $\frac{B}{2} = 7$ $B = 14$。

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