**Question:**

A car travels 1 kilometre distance in which each wheel makes 450 complete revolutions. Find the radius of the its wheels.

**Solution:**

Let the radius of wheel be *r*. Thus, circumference *C* of the wheel

$C=2 \pi r$

Since car travels 1 km distance in which wheel makes 450 complete revolutions. Then

The distance covered by wheel in one revolution $=\frac{\text { Distance moved }}{\text { Number of revolution }}$

$=\frac{1000 \mathrm{~m}}{450}$

$=\frac{20}{9} \mathrm{~m}$

We know that,

The distance covered in one revolution $=$ circumference of the wheel

$\frac{20}{9}=2 \times \frac{22}{7} \times r$

$r=\frac{20 \times 7}{9 \times 2 \times 22}$

$=0 . \overline{35} \mathrm{~m}$

$=35.35 \mathrm{~cm}$

Hence the radius of wheel is $35.35 \mathrm{~cm}$.

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