Direct and Inverse Proportions

Question

Tap A can fill 8 pails of the exact capacity in 5 minutes.

Tap B can fill 7 of the same pails in 4 minutes.

Tap A and B are turned on together to fill a total of 16 pails.

How long will it take the two taps to fill the 16 pails together? Give your answer in minutes and seconds to the nearest second

Answer 1

A fills 8 in 5 minutes

B fills 7 in 4 minutes

A&B fills 16 in how long?

A fills 8/5 in 1 minute

B fills 7/4 in 1 minute

together they fill 8/5 +7/4 = 67/20 in 1 minute

they together fill 16 in 16/(67/20) = 16(20/67) = 320/67 = 4.7761 minutes

= 4 minutes and 47 seconds