Question

A pipe can empty the tank in 40 minutes a second pipe with a diameter twice that much as

Answer 1

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Answer 2

A pipe can empty a tank in 40 minutes. A second pipe with diameter twice as much as that of the first is also attached with the tank to empty it. The two pipe together can empty the tank in:

A) 8 minutes

B) 1313
13
1
3
minutes

C) 30 minutes

D) 38 minutes

Correct Answer:
A) 8 minutes

Description for Correct answer

Pipe A : Pipe B

Diameter D : 2D

π(D2)2:π(2D2)2
π
(
D
2
)
2
:
π
(
2
D
2
)
2


π D24:π D2
π

D
2
4
:
π

D
2


π D2:4π D2
π

D
2
:
4
π

D
2




(A+B)
(
A
+
B
)
empties in

=404+1
40
4
+
1


=8 minutes