Question

Tiana can clear a football field of debris in 3 hours. Jacob can clear the same field in 2 hours. If they decide to clear the field together, how long will it take them?

A.) 50mins
B.) 1hr 5mins
C.) 1hr 12mins
D.) 5hrs

Answer 1

6/5 hr, or 1 hr 12 min

Explanation:

We're looking for the time required for two people to clear a field.

We'll end up with an expression that looks like:

1 job

------------ = time

rate

or

1 job

------------- this has dimensions of time (hr).

1 job/hr

specifically, we evaluate the following expression:

1 job

--------------------------------

1 job 1 job

-------- + --------

3 hr 2 hr

This simplifies to

1 1

-------------- = ----------- = 6/5 hr, or 1 hr 12 min

1/3 + 1/2 5/6