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?
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A 1 step stair case requirest 4, 2 step 10, so we need 6 more. 2-3 step needs 8 more,so following the pattern we get 10 toothpicsk from 3-4, 12 from 4-5.
10+12 = 22.
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