Question

7. The diameter of a wheel of a bus is 90 cm which makes 315 revolutions per
Determine its speed in kilometres per hour. [Use = 22/7]
​

Answer 1

Solution:

Given:

=> Diameter of wheel = 90 cm

=> Radius of wheel = 45 cm

To Find:

=> Speed

Formula used:

$\sf{\implies Circumference\;of\;wheel = 2\pi r}$

So,

=> Distance covered in 1 revolution = Circumference of wheel = 2πr

$\sf{\implies 2\times \dfrac{22}{7} \times 45\;cm}$

$\sf{\implies \dfrac{1980}{7}\;cm}$

So,

$\sf{\implies Distance\;covered\;in\;315\;revolutions = \dfrac{1980}{7}\times 315\;cm}$

$\sf{\implies 89100\;cm}$

$\sf{\implies 891\;m}$

Hence, the speed is 891 m/min. So we will change into km/h.

$\sf{\implies \dfrac{891}{1000}\times 60\;kr/hr}$

$\sf{\implies \dfrac{5346}{100}\;km/hr}$

$\sf{\implies 53.46\;km/hr}$

$\large{\boxed{\boxed{\green{\sf{\implies So,\;Speed=53.46\;km/hr}}}}}$

Answer 2

${\bold{\underline{\underline{Answer:}}}}$

${\bold{\therefore Speed\:of\:bus=53.46\:km/h}}$

${\bold{\underline{\underline{Answer:}}}}$

• In the given question information given about diameter of a wheel of a bus is 90 cm which makes 315 revolutions.

• We have to find its speed in kilometres per hour.

$\underline \bold{Given : } \\ \implies Diameter \: of \: weel = 90 \: cm \\ \\ \implies No. \: of \: revolution = 315 \\ \\ \underline \bold{To \:Find :} \\ \implies Speed \: of \: bus = ?$

• According to given question :

$\implies Diameter = 90 \: cm \\ \bold{ \implies Radius = \frac{90}{2} = 45 \: cm} \\ \\ \bold{Finding \: Circumference \: of \: circle : } \\ \implies Circumference = 2\pi r \\ \\ \implies Circumference = 2 \times \frac{22}{7} \times 45 \\ \\ \bold{\implies Circumference = \frac{1980}{7} { cm}^{2} } \\ \\ \bold {Area \: covered \: in \: 315 \: Revolution : } \\ \implies \frac{1980}{ \cancel7} \times \cancel{315 }\\ \\ \implies 1980 \times 45 \\ \\ \implies 89100 \: cm \\ \\ \bold{\implies 891 \: m} \\ \\ \bold{For \: Speed \: of \: bus : } \\ \implies Speed = \frac{891}{1000} \times 60 \\ \\ \implies Speed = 8.91 \times 6 \\ \\ \bold{\implies Speed = 53.46 \: km/h} \\ \\ \bold{\therefore \: Speed \: of \: bus \: is \: 53.46 \: km/h}$