Question

(145. Valve A can fill a sump in 16
hours and valve B can fill the same
sump in 10 hours. Only valve A is
opened first.(After how many hours
should valve B be opened so that the
time taken to fill the sump is 8 hours?
a. 1 h b. 2 h c. 3 h d. 4 h​

Answer 1

After 3 hrs  Valve B should be opened  , if Valve A can fill a sump in 16 hours and valve B can fill the same sump in 10 hours.

Step-by-step explanation:

Valve A can fill a sump in 16 hours

=> Valve a can fill in 1 hr = 1/16

valve B can fill the same sump in 10 hours

=> Valve B can fill in 1 Hr = 1/10

Valve A is opened first  => Vallve a will work for 8 hrs

Valve B opened after x hours then Valve B will work for 8-x hrs only

8 * (1/16)  + (8-x)/10  = 1

=> 1/2 + (8-x)/10 = 1

multiplying by 10 both sides

=> 5 + 8 - x = 10

=> x = 3

After 3 hrs  Valve B should be opened

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