AMC10 2015 A

AMC10 2015 A · Q3

AMC10 2015 A · Q3. It mainly tests Arithmetic misc, Basic counting (rules of product/sum).

Ann made a 3-step staircase using 18 toothpicks as shown in the figure. How many toothpicks does she need to add to complete a 5-step staircase?

Ann 使用 18 根牙签做了一个 3 级楼梯，如图所示。要完成一个 5 级楼梯，她还需要添加多少根牙签？

(A) 9 9

(B) 18 18

(D) 22 22

(E) 24 24

Answer

Correct choice: (D)

正确答案：（D）

Solution

Answer (D): Five vertical and five horizontal toothpicks must be added to complete the fourth step. Six vertical and six horizontal toothpicks must be added to complete the fifth step. This is a total of 22 toothpicks added.

答案（D）：完成第四步必须添加五根竖直牙签和五根水平牙签。完成第五步必须添加六根竖直牙签和六根水平牙签。总共添加了22根牙签。

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