AMC 10A 2015 Problem 3

Past Contests AMC 10 2015 Part A
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1

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?

Answer Choices
A. 9
B. 18
C. 20
D. 22
E. 24

Image