Question

Pipe a and b can fill the tank in 6 minutes and 7 minute repectively. Starting from tap a each taps are opeend alternate for 1-1 minute

Answer 1

Answer:

Approx time = 6.46 mins

Actual time = 6.43 mins

Step-by-step explanation:

Pipe a fill tank in 6 minute

Tank filled by pipe a in 1 minute = 1/6

Pipe b fill tank in 7 minute

Tank filled by pipe b in 1 minute = 1/7

Every two minutes tank will be filled = (1/6 + 1/7)

= (7+6)/42

= 13/42

Approx Time for filling the tank approx (42*2)/13 = 84/13 mins = 6.46 min (more than 6 mins but less than 7 mins) (it means pipe a & b will not run for same time )

so pipe b will run for 3 mins but pipe a will run for more than 3 mins

Tank filled by b in 3 mins = 3/7

Remaining tank = 1 - 3/7 = 4/7

Time taken by pipe a to fill 4/7 tank = (4/7) * 6 = 24/7 = 3.43 mins

total time taken = 3 + 3.43 = 6.43 mins