Hana builds a fence using sticks. Step 1 uses 5 sticks. Each new step adds 4 more sticks. She uses a total of 81 sticks. How many steps did she build?
Need a hint?
Count the first step separately before you divide by the number of sticks added at each new step.
Worked answer
- Sticks in Step 1 = 5, so the first step is not repeated.
- Sticks left after Step 1 = 81 - 5 = 76.
- Each later step adds 4 sticks, so later steps = 76 ÷ 4 = 19.
- Total steps = 19 + 1 = 20.
Answer: 20 steps
The mistake this question tests
Habit
Calculation slip
Pupils divide 81 by 4 straight away, which treats Step 1 as if it added 4 sticks. Subtract the 5 sticks of Step 1 first, then divide by 4, and add 1 for Step 1.
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