Question

A bicycle wheel, diameter 56 cm, is making 45 revolutions in every 10 seconds. At what speed, in kilometre per hour, is the bicycle travelling?

Answer 1

Diameter =56 cm

$\therefore$ Radius, r =28 cm

$\therefore$ Distance travelled in 1 revolution

i.e. circumference $=2\pi r=2\times \frac{22}{7}\times 28=176cm$

$\therefore$ Distance travelled in 45 revolutions

$=176\times 45=7920cm=\frac{7920}{100\times 1000}km$

Time =10 sec $=\frac{10}{60\times 60}hr.$

Speed $=\frac{\frac{7920}{100\times 1000}}{\frac{10}{60\times 60}}m$

$=\frac{7920}{100\times 1000}\times \frac{60\times 60}{10}=\frac{28512}{1000}km/hr$

=28.512 km/hr