At a salt mine one conveyer belt requires 20 minutes to fill a large truck with ore and the second requires 30 minutes

Question

How long would it take both conveyor belts working together to fill the truck with ore

Answer 1

To find the time working together, put the times in the denominators, using this equation:

 

1/20 + 1/30 = 1/x

 

 

Now solve for x - Start by getting a common denominator:

 

3/60 + 2/60 = 1/x

 

5/60 = 1/x

 

Cross multiply:

 

5x = 60

 

 

x = 12