Question

The area of a circular field is 88704 sq. m. How long will it take to go round 10 times at the speed of 4.5 km per hour?

• A. 2.34 hrs
• B. 3.24 hrs
• C. 4.28 hrs
• D. 2.34 hrs

Answer 1

The correct option is A

2.34 hrs

Let r m be the radius of the circular field

Area of field is 88704 sq. m (given in the question)

$\pi r^2$ = 88704 sq. m

$\Rightarrow r^2$ = 88704 $\times \left(\frac{7}{22}\right)$

$\Rightarrow r^2$ = 28224 $m^2$

$\Rightarrow$ r = 168 m

Also, circumference of circle = $2\times \left(\frac{22}{27}\right)\times 168m$

= 1056 m

Distance covered in 10 rounds = 10 $\times$ circumference of circular field

= 10 $\times$ 1056 = 10560 m.

Time taken = $\frac{Distance}{Speed}$

$=\frac{10.560km}{4.5km/hr}$

= 2.34 hrs