Pipe A can fill a tank in 30 mins and Pipe B can fill it in 28 mins If 3

pipe A fill 1/30 in 1 mnt.
similarly pipe B fill 1/28 in 1mnt
3/4th part is filled by pipe B alone.
so time taken by pipe B to fill 3/4th part will be.
( 1/28 ---------- 1mt
3/4 ----------- x mnt
by cross multiplication
1/28 * x =3/4
so x=(28*3)/4 = 21 mnts)
so B takes 21mnts to fill 3/4th part alone...
now the remaining part is
1-3/4 = 1/4.
now, (A+B)'s 1mnt work = 1/30 + 1/28 = 29/420.
therefore time taken by both pipes to fill 1/4th part together will be..
( 29/420-------- 1mnt
1/4----------- x mnt
by cross multiplication
x = 420/(29*4)
x= 105/29 = 3.62 mnts)..
so the total time taken by both the pipes to fill the tank is
(time taken by pipe B to fill 3/4th part + time taken by both pipe to fill 1/4th part)
21+3.62=24.62 mnts
10 years agoHelpfull: Yes(21) No(1)
time required by pipe A=1/4/1/30=30/4
time required by pipe B=3/4/1/28=21
so total time required=30/4+21=28.5
12 years agoHelpfull: Yes(9) No(25)
T w
A 30 28
840
B 28 30

1-3/4=1/4

840/4=210 (remain work)

210/(30+28)=3.62min
7 years agoHelpfull: Yes(0) No(0)

Pipe A can fill a tank in 30 mins and Pipe B can fill it in 28 mins.If 3/4th of the tank is filled by Pipe B alone and both are opened, how much time is required by both the pipes to fill the tank completely ?