04 Try it yourself Interactive

Two or three workers, no fractions

Give each person the number of days they need alone. The console picks the LCM as the job size, converts each time into a whole-number rate, adds the rates and divides. Set C’s days to zero for a two-person question. Notice that the together time is always below the fastest individual time.

A in 10 days, B in 15 days
30 units · 6 days
The LCM is chosen so every rate is a whole number. That is the only reason it is used — any job size gives the same final answer.
Press Next to work through it one step at a time.
Total units–
Units/day–
Together–
Answer–
step 0 / 0