20.A tyre has punctures. The first puncture alone would have made the tyre flat in 9 minutes and the second alone would have done it in 6 minutes. If air leaks out at a constant rate, how long does it take both the punctures together to make it flat?
A. 1x1/2 minutes B. 3x1/2 minutes
C. 3x3/5 minutes D. 4x1/4 minutes
Answer:
1 minute's work of both the punctures = (1/9+1/6)
= 5/18
So, both the punctures will make the tyre flat in = 18/5
= 3x3/7 days
