Question

3. How long will a man take to make a round of a circular field of radius 21 m, cycling at the
speed of 8 km/h?
​

Answer 1

hope it will help getting the concept.

Answer 2

$\huge\sf\pink{Answer}$

☞ Your Answer is 5.94 sec or 2 min in approx

━━━━━━━━━━━━━

$\huge\sf\blue{Given}$

✭ Radius of circle is 21 m

✭ A man is comming round the circle with a speed of 8 km/h

━━━━━━━━━━━━━

$\huge\sf\gray{To \:Find}$

◈ The time taken?

━━━━━━━━━━━━━

$\huge\sf\purple{Steps}$

Circumference of a circle is given by,

$\underline{\boxed{\sf Circumference_{circle} = 2\pi r}}$

Substituting the given values,

»» $\sf Circumference_{circle} = 2\pi r$

»» $\sf 2 \times \dfrac{22}{7} \times 21$

»» $\sf 2 \times 22 \times 3$

»» $\sf \green{Circumference = 132 \ m^2}$

So now we shall conver the speed of the person from km/h to m/s

➳ $\sf Speed = 8 \ km/h$

➳ $\sf 8\times \dfrac{5}{18}$

➳ $\sf \red{Speed = 2.22 \ m/s}$

We know that,

$\underline{\boxed{\sf Speed = \dfrac{Distance}{Time}}}$

Substituting the values,

➝ $\sf Speed = \dfrac{Distance}{Time}$

➝ $\sf Time = \dfrac{Circumference}{Speed}$

➝ $\sf Time = \dfrac{132}{2.22}$

➝ $\sf \orange{Time = 59.45 \ sec}$

━━━━━━━━━━━━━━━━━━