A tyre has two punctures. The first punctures alone would have made the tyre flat in 45 minutes, and the second puncture alone would have done it in 90 minutes. If air leaks out at a constant rate, then how long (in minutes) does it take for both the punctures together to make the tyre flat?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 30
Given:
The first puncture alone would have made the tyre flat in 45 minutes.
The second puncture alone would have done it in 90 minutes.
Concept Used:
Total work = Efficiency × time taken
Explanation:
Let the total work be LCM of (45 and 90) = 90 units
Efficiency of 1st puncture (90/45) = 2 units/min
Efficiency of 2nd puncture (90/90) = 1 unit/min
Effective efficiency of both the puncture = 3 units/min
Time taken to flat the tyre by both the puncture = 90/3 = 30 min