1 Answers
Option 3 : 5 hours
Given, tap A is 40% more efficient than tab B
∴ The ratio of efficiency of A : B = 7 : 5
Total time taken by A alone to fill the tank = 4D hours
∴ Total time taken by B alone to fill the tank = 7/5 × 4D hours = 5.6D hours
Time taken by B alone to fill 3/4th of the tank = 4.2D hours
According to the question,
4.2D = D + 16
⇒ D = 5 hours
∴ Total time taken by A alone to fill the tank = 4 × 5 = 20 hours
Total time taken by B alone to fill the tank = 5.6D = 28 hours
Let the total capacity of the tank be LCM of (20 and 28) = 140
Number of units filled by A in 1 hour = 140/20 = 7
Number of units filled by B in 1 hour = 140/28 = 5
Let the number of hours for which A and B didn’t work with their full efficiency be ‘x’ hours
Now, according to the question,
⇒ x + × 10 = 140
⇒ 4x + 10 × 12 = 140
⇒ x = 5 hours