A garden roller is a cylinder with a radius of 7 cm. It rolls along a path without slipping. How far does it travel in 15 complete rolls? (Take π = 227)
- 22 cm
- 44 cm
- 330 cm
- 660 cm
Need a hint?
Find the distance for one complete roll first, then multiply by the number of rolls.
Worked answer
- One complete roll covers the circumference of the roller.
- Circumference = 2 × π × radius = 2 × 227 × 7 = 44 cm.
- Distance for 15 rolls = 15 × 44 cm = 660 cm.
Answer: 660 cm
The mistake this question tests
Habit
Radius and diameter in circles
Using the radius instead of the circumference gives 22 cm per roll, or 15 × 22 = 330 cm when the formula is written as π × radius instead of 2 × π × radius.
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