Question

A girl while walking diametrically across a semicircular playground, takes 3 minutes less than if she had kept walking around the circular path from A to B. If she walks 60 metres a minute, what is the diameter of the playground?

• A. 60m
• B. 48m
• C. 84 m
• D. 315m

Answer 1

The correct option is D 315m


Let the radius be r, then diffrerence in the distance
$=(\pi r-2r)=r(\pi -2)$
$=r(\frac{22}{7}-2)=60\times 3$
$\Rightarrow 2r=315m$
[$\pi r$ $\to$ semiperimeter and $2r\to$ diameter]