it takes a printer 10 hours to print the schedules. A faster printer can do the job in 6 hours. How long will it take to to do the job if both printers are used?

3h45

Step-by-step explanation:

The first printer, in one hour, can do 1/10 of the whole job.

The second printer, in one hour, can do 1/6 of the job.

When we add these together, we find out what both printers can do together in one hour : 1/10 + 1/6

Now find a common denominator ... = 4/15

Together, the printers can do 4/15 of the work in one hour.

The time for the entire job is represented by the reciprocal of what can be done in one hour, so the total job can be done in ... 15/4 hours which means 3 hours and 45 mins