Help solving problem

Question

one printer can print the paychecks for the employees of a company in 60 min. a second printer can print the checks in 90 min. how long would it take to print the checks in 90 min. how long would it take to print the checks with both printers operating?

Answer 1

working together they can do it in X minutes where

1/60 + 1/90 = 1/X

3/180 + 2/180 = 1/X

5/180 = 1/X

1/36 = 1X

X=36 minutes working together

if both did it in 60 minutes each, together they'd do it in half the time or 30 minutes

if both did it in 90 minutes each, then together they'd do it in half the time or 45 minutes

You know if one does 60 and the other 90, together they'd do it in somewhere between 30 and 45 minutes