A can go round a circular path 8 times in 40 minutes. If the diameter of the circle is increased to 10 times the original diameter, then the time required by A to go round the new path once, travelling at the same speed as before is	Choose the correct choice from the following answers: A) 20 min B) 35 min C) 50 min D) 70 min E) none
Solution   Let original diameter be d metres. Then, its circumference = (Πd)metres.   Time taken to cover (8Πd)m = 40 min.   New diameter = (10d)m. Then, its circumference = (Π x 10d)m.   Time taken to go round it once   ‹=› [40 / 8Πd x 10Πd]m   ‹=›50 min.   Answer 50 min
<result>C</result>
A can go round a circular path 8 times in 40 minutes. If the diameter of the circle is increased to 10 times the original diameter, then the time required by A to go round the new path once, travelling at the same speed as before is