Bunuel wrote:
Two circles, one with radius 10 inches and the other with radius 4 inches, are tangent at point Q. Two insects start crawling at the same time from point Q: one along the larger circle at 3π inches per minute, the other along the smaller circle at 2.5π inches per minute. How much time has elapsed when the two insects meet again at point Q?
(A) 15 minutes
(B) 30 minutes
(C) 40 minutes
(D) 1 hour
(E) 1 hour, 20minutes
Time taken by insect 1 to cover one circle and come back to Q = Circumference of circle/Speed = 20π/3π = 20/3 min
Time taken by insect 2 to cover one circle and come back to Q = Circumference of circle/Speed = 8π/2.5π = 16/5 min
So insect 1 will come to Q every 20/3 min and insect 2 will come to Q every 16/5 mins.
Think about it. Had these numbers been simpler e.g. insect 1 comes to Q every 5 mins and insect 2 comes to Q every 4 mins, when will they meet at Q again? After 20 mins. Why? Because insect 1 will come at 5 min, 10 min, 15 min, 20 min etc marks and insect
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Statistics : Posted by KarishmaB • on 28 Oct 2021, 05:30 • Replies 6 • Views 3415
