Question 100038
Let t=time it takes both working together
Kim unloads at the rate of 1/20 delivery truck per minute

Rom unloads at the rate of 1/35 delivery truck per minute

Together, they unload at the rate of (1/20+1/35 or 11/140) delivery trucks per min

1/20+1/35= The LCM is 140.  Multiply both sides by 140/140

7/140+4/140=11/140

So our equation to solve is:

(11/140)*t=140/140-------(note 140/140 denotes one delivery truck)

Multiply both sides by 140
11t=140  divide both sides by 11

t=12.73 min---------------------time it takes both working together

CK
(1/20)*12.73+(1/35)*12.73=1
0.636363+0.363636=1
~1=~1


Hope this helps---ptaylor