Question

two pipes p and q would fill an empty cistern in 24 minutes and 32 minutes respectively. Both the pipes being opened together find when the first pipe must be turned off so that the empty cistern may be just filled in 16 minutes

Answer 1

:
let t = on time of the 1st pipe to accomplish this
let the completed job = 1 (a full cistern)
:


each will do a fraction of the filling, the two fractions add up to 1
 +  = 1
reduce the 2nd fraction
 +  = 1
multiply equation by 24, cancel the denominators
t + 12 = 24
t = 24 - 12
t = 12 min, then turn the 1st pipe off

Answer 2

Answer:

t = 12

Step-by-step explanation:

:

let t = on time of the 1st pipe to accomplish this

let the completed job = 1 (a full cistern)

:

each will do a fraction of the filling, the two fractions add up to 1

+  = 1

reduce the 2nd fraction

+  = 1

multiply equation by 24, cancel the denominators

t + 12 = 24

t = 24 - 12

t = 12 min, then turn the 1st pipe off