Aptitude - Pipes and Cistern - Discussion

The tap can fill half the tank in 3 hours i.e, in 180 min,
Then 4 taps can fill half the tank in 180/4 = 45 min,
Total: 3 hours 45 min.

Simple.

Tank takes to fill within 6 hours. So half of the tank we stop the waterfall. So half tank fills times 3 hours. So remaining half tank we use 4 pipes. Each pipes s similar so each pipe takes 3 hours to fill the tank. But here we open together all pipes.

The remaining 3 hours will be reduced by 4 pipes. 3 hours =180mins.
So we know 180/4 pipes = 45mins. So already half tank is filled.
Remaining the half tank has been filled withn 45 mins so, 3hours 45 mins is the answer.

A tap can fill a tank in 6 hours.

So, 1/2 of the tank is filled in 3 hours.
Now part of the tank filled by 4 same types of taps in 1 hour is (4 x 1/6) = 2/3,
This means 2/3 part is filled by 4 taps in 1 hr,
So 1 part is filled in 3/2 hr,
So 1/2 part is filled in 3/2 x 1/2 = 3/4 hr = 45 min.

Hence total time taken is 3 hr 45 min.

Thanks @Faysal.

Given A tap can fill a tank in 6 hours.

After half the tank is filled i.e. after 3 hrs.

three more similar taps are opened i.e.

no. of taps to fill remaining half tank = 4 taps

when 1 tap is used = (3 hrs/1 tap)

when 4 taps are used = (3 hrs/4 taps)=45min

total= 3hrs+45min

Good explanation, Thanks. @Vicky!

Tank filled in 1hr =6units.
For half an hour =3units.
Remaining 3units.
Now 3 more taps.....+previous 1 tap =4taps.
Efficiency =3/4.
Total =3*3/4(60)=3hr 45min.

Simple (3hour/1pipe)+(3hour/4pipe).
(First hf tank)+(sec half tank) = 3(3/4) = in hours then = 3(3*60)/4 = 3hr 45min.

Thanks @vicky.

One tap can fill the whole cistern in = 6 hr,
And half(1/2)tank can fill in = 3 hr.

Remaining (1/2)tank will filled with the 4 pipes(1+3) = 3hr = 180min,
4 pipes = 180/4 = 45min.

So the final answer is (1half+2nd half) = 3hr + 45min,
3hr and 45min.