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. 50 minutes
B. 1 hour 5 minutes
C. 1 hour 12 minutes
D. 5 hours

Answer 1

As  Tiana can clear the field in 3 hours,
 
it means she can clear in 1/3 per hour

Also, Jacob can do 1/2 of the work per hour. 

now the rate we will determine when they are working together
so

hours are for completing:
Tiana = 3
Jacob = 2
Together = t have to find
so
Work done per hour:
Tiana = 1/3
Jacob = 1/2
Together = 1/t

by adding their work together 
it will be
1/3 + 1/2 = 1/t now solve it

5/6 = 1/t
t = 6/2 = 1.2

1.2 hours they can clear the field
hope it helps