Question

the diameter of a cylcle wheel is 21cm.how many revolution will it make to travel 1.98km?

Answer 1

distance to be travel= 1980m
perimeter= 3.14*(0.21)= 0.6594m
revolution=1980/0.6594
revolution=3002.72 revolutiona

Answer 2

$\bf{Diameter }$= 21 cm

$\bf{Radius}$ =21/2 cm

Circumference of the wheel = 2πr

$= 2 \times \frac{22}{7} \times \frac{21}{2}$

$= \cancel 2 \times \frac{22}{ \cancel7} \times \frac{ \cancel{21} \: \: 3}{ \cancel2}$

=22×3

=66 cm

$\bf{Distance \:covered}$= 1.98 km

= 1.98 × 1,00,000

=198000 cm

$\bf{No. \:of \:revolution}$
$= \bf{ \frac{distance \: covered}{circumference} }$

$= \bf{ \frac{198000}{66} }$

$= 3000$

$\textbf{So , number of revolution=3000}$