Working together, two pumps can drain a certain pool in 4 hours. if it takes the older pump 12 hours to drain the pool by itself, how long will it take the newer pump to drain the pool on its own?
Do not do any rounding.

Question

Working together, two pumps can drain a certain pool in 4 hours. if it takes the older pump 12 hours to drain the pool by itself, how long will it take the newer pump to drain the pool on its own?
Do not do any rounding.

anonymous · Answer

This seems easy but it is mindfu*king me

anonymous · Answer

haha right?

anonymous · Answer

attachment

anonymous · Answer

it's those steps, but i got it wrong when i tried it...

anonymous · Answer

@bbbbbbbbbbbbbbbbbb

wolf1728 · Answer

Formula is:

4 Hours = Pump1 * Pump2 / (Pump1 + Pump2)
4 hours = 12 * pump2 / (12 + Pump2)
4 * Pump2 + 48 = 12*pump2
48 = 8 * pump2
pump2 = 6 hours

Double Check
Both working together
(12 * 6) / (12 + 6)
72 / 18
= 4 hours

anonymous · Answer

Left on together, the cold and hot water faucets of a certain bathtub take 5 minutes to fill the tub. If it takes the cold water faucet 15  minutes to fill the tub by itself, how long will it take the hot water faucet to fill the tub on its own?
Do not do any rounding.
What about this one ? 

And thank you @wolf1728 !!

wolf1728 · Answer

Both faucets = 5 minutes
cold faucet = 15 minutes

5 = 15 * hot / (15 + hot)
75 + 5 * hot = 15 * hot
75 = 10 * hot
hot faucet = 7.5 hours

Double Check
Both faucets
(15*7.5) / (15+7.5)
112.5 / 22.5
= 5 minutes !!

successful !!!

wolf1728 · Answer

Gee? Any chance for a medal ???

anonymous · Answer

Sorry I had to step away. But much appreciated! thank you so much!! :D