Question

solve this question .​

Answer 1

$\large\sf\underline{\underline{\red{Question}}}:$

• The wheels of a car are of diameter 80 cm each. How many complete revolutions does each wheel make in 10 minutes when the car is travelling at a speed of 66 km per hour?

$\large\sf\underline{\underline{\red{Solution}}}:$

We know that,

$\green\bigstar\boxed{\sf Circumference_{\green{Circle}}= 2\pi r \;\;or\;\;\pi d}$

Where,

• r is radius
• d is diameter.

$\longmapsto \bf Circumference_{\green{Circle}} = \pi 80 = 80\pi$

Distance covered by wheel in 1 revolution is 80π cm.

$\green\bigstar\boxed{\sf speed = \dfrac{distance}{time}}$

• Distance = speed x time

Converting 66km/h to cm/min.

• $\dfrac{66\times 100000}{60} = 110000 cm/min$ [1km = 100000 cm.]

Distance covered in 10 min ,

• 110000 x 10 = 1100000 cm

so,

$\longmapsto \bf No. \; of\; revolutions = \dfrac{Total\;distance}{distance\;covered\;in\;1\;revolution}$

$\longmapsto \bf No. \; of\; revolutions = \dfrac{1100000}{80\pi}$

$\longmapsto \bf No. \; of\; revolutions = \dfrac{110000\cancel{0}\times 7}{8\cancel{0}\times 22}$

$\longmapsto \bf No. \; of\; revolutions = \dfrac{770000}{8}$

$\longmapsto \bf No. \; of\; revolutions = 4375$

Hence,

• Each wheel of car will make 4375 revolutions in 10 minutes.