Pipes A and B can fill a storage tank in 8 hours and 12 hours, respectively. With the tank empty, pipe A was turned on at noon, and then pipe B was turned on at 1:30 P.M. At what time was the tank full?

Question

Pipes A and B can fill a storage tank in 8 hours and 12 hours, respectively.  With the tank empty, pipe A was turned on at noon, and then pipe B was turned on at 1:30 P.M.  At what time was the tank full?

anonymous · Answer

no one likes these questions i see

amistre64 · Answer

this is an easier one tho :)

anonymous · Answer

ok an hour and a half for pipe A that fill the tank in 8 hours, means its rate is 1/8 per hour and 
$$1.5\times \frac{1}{8}=\frac{3}{16}$$ meaning the tank is 
$$\frac{3}{16}$$ full at one thirty.  the two pipes together work at a rate of 
$$\frac{1}{8}+\frac{1}{12}=\frac{5}{24}$$ of the tank per hour.  
now solve 
$$\frac{3}{16}+\frac{5}{24}x=1$$ for x

anonymous · Answer

did other annoying refund one too, but i think they have left already

amistre64 · Answer

yeah, its a thankless job eh ;)

anonymous · Answer

did i do this right because i get 3.9 usually problems cooked to nice integer solutions