AMC8 2004

AMC8 2004 · Q6

AMC8 2004 · Q6. It mainly tests Percent, Averages (mean).

After Sally takes 20 shots, she has made 55% of her shots. After she takes 5 more shots, she raises her percentage to 56%. How many of the last 5 shots did she make?

Sally 投了 20 次后，她的命中率为 55%。再投 5 次后，她的命中率提高到 56%。她在最后 5 次投篮中命中了几次？

(A) 1 1

(B) 2 2

(D) 4 4

(E) 5 5

Answer

Correct choice: (C)

正确答案：（C）

Solution

(C) If Sally makes 55% of her 20 shots, she makes $0.55 \times 20 = 11$ shots. If Sally makes 56% of her 25 shots, she makes $0.56 \times 25 = 14$ shots. So she makes $14 - 11 = 3$ of the last 5 shots.

（C）如果 Sally 在 20 次投篮中命中 55%，那么她命中 $\0.55 \times 20 = 11$ 次。如果 Sally 在 25 次投篮中命中 56%，那么她命中 $\0.56 \times 25 = 14$ 次。因此她在最后 5 次投篮中命中 $14 - 11 = 3$ 次。

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