Question

Person 1 can do a certain job in 21 minutes, and person 2 can do the same job in 28 minuets. When completing the job together, which expression would be used to represent the amount of work done by person 1. 21,1/21,x/21,21x

Answer 1

Answer:

1/21.

Step-by-step explanation:

To solve the problem 'How long would they take to do the job working together?'  you would work in fractions of the job done / minute:

1/21 + 1/28 = 1/x.

So for person 1 the expression is 1/21.