Billys bike has wheels of a diameter 90cm. He has invented a counter for his bike, which counts the number of revolutions the wheels make. One day the counter shows 210 revolutions. How far has Billy.

Question

1. This is a maths question

Answer 1

In this problem you need to know the relationship between the diameter and the circumference. The relationship is that C = π x D. An easy way to remember that is that it rhymes. Pi X Di

You can express the circumference in terms of pi to make the initial calculations easier.

So the first step is to understand that C is 90 π.

The counter indicates that the tire has rotated 210 times. To find the total distance that the tire has traveled you must multiply the circumference of the tire (90 π) by 210.

90 x 210 x π = 18,900 π

Once you complete the math, you must remember the units...you don't mean 18,900 π apples. If you want to be understood you must remember the original problem and not neglect the units!

18,900 π cm is the most precise answer but is probably not practical if you are biking around the neighborhood. In a practical application it would be best to either use the π button on a calculator or if you don't have a calculator, use 3.14 as a value for π.

Final answer will be an approximation: 59, 376 cm.

Actually, this does not take into consideration significant figures....but that's another lesson. : )