Question

Person 1 can do a certain job in fifteen minutes, and person 2 can do the same job in thirty minutes. When completing the job together, which expression would be used to represent the amount of work done by person 1?

Answer 1

Quantity = work × time

Answer 2

The expression used to represent the amount of work done by person 1 is 1/15, whereas when it comes to person 2 it is 1/30.
You use 1/15 since it is the fifteenth of one hour.