It takes 7 minutes to fill a bathtub using coldwater faucet alone. It takes 12 minutes using the hot water faucet alone. How long will it take to fill the tub using both?

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Answer 1 · 2016-08-16T19:18:23

By using both the faucets bathtub gets filled in #4.42# minutes

By cold water faucet #7# minutes to fill #1# bathtub

or

#1# minute to fill #1/7# bathtub
Similarly;
By hot water faucet #12# minutes to fill #1# bathtub

or

#1# minute to fill #1/12# bathtub

By using both we can write
#1# minute to fill #(1/7+1/12)# bathtub

or

#1 #minute to fill #(1/7+1/12)# bathtub

or

#1# minute to fill #((12+7)/84)# bathtub

or

#1# minute to fill #((19)/84)# bathtub

or

#((19)/84)# bathtub gets filled in #1# minute

or

#1# bathtub gets filled in #84/19# minutes

or

#1# bathtub gets filled in #4.42# minutes

Therefore by using both the faucets bathtub gets filled in #4.42# minutes