Question

A local dairy has three machines to fill half-gallon milk

cartons. The machines can fill the daily quota in 5
hours, 6 hours, and 7.5 hours, respectively. Find how
long it takes to fill the daily quota if all three machines
are running.

Answer 1

Explanation:

let's assume the quota is 1

1=the time each machine takes to fill the quota thus;

1=5hrs what about 1hr=1/5

1=6hrs what about 1hr =1/6

1=7.5hr what about 1hr =2/15

add: 1/5+1/6+2/15=1/2 reciprocate

=2hrs