Symbiosis National Aptitude Test SNAP 2019 Paper

Question : 63 of 110

Marks: +1, -0

Valve A fills a bathtub in 10 hours and valve B fills the same bathtub in 15 hours. A and B are opened together, and later B was closed after some time. Total time taken to fill the bathtub is 8 hours. For how long B was open?

1 hour
2 hours
3 hours
4 hours

Validate

Solution:

Value A fills bathtub in 10 hours
Value B fills bathtub in 15 hours
L.C.M. of 10 and 15 = 30
Work done by value A in 1 hour =

{30}/{10}

= 3 units
Work done by value B in 1 hour =

{30}/{15}

= 2 units
Let value B was open for t hours
then, 3 × 8 + 2 × t = 30
24 + 2t = 30
t = 3 hours
Hence, valve B was open for 3 hours.

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