Chiru while walking diametrically across a semi-circular playground takes 6 min less than if he had kept running around

Chiru while walking diametrically across a semi-circular playground takes 6 min less than if he had kept running around the circular path from P to Q. If he run 25 meter in 50 sec. what is the radius of the playground?

a) 155.5 m

b) 156.5m

c) 157.5 m

d) 158.5 m

Sol: