word problem

Question

If pipe a takes 8 hours to fill a tank and pipe b takes 12 hours and pipe a starts filling the tank at noon and pipe b starts at 1:30 what time is the tank filled

Answer 1

In one hour A fills 1/8 of the tank. After 1.5 hours (noon to 1:30), A fills 3/16 of the tank. Only 13/16 remain.

In one hour B fills 1/12 of the tank.

 

In the x hours remaining A fills x/8 of the tank.

In the x hours remaining B fills x/12 of the tank.

 

x/8 + x/12 = 13/16             LCD is 48

6x + 4x = 13(3)

10x = 39

x = 3.9