Lisa can shovel snow from her driveway in 45 minutes. Jim can do the same job in 35 minutes. How long will it take Lisa and Jim to shovel the driveway if they work together?

Answer: it takes Lisa and Jim 19.6785 hours to shovel the driveway

Step-by-step explanation:

It takes Lisa 45 minutes to shovel snow from her driveway. This means that her unit rate of working in terms of time is 1/45

It takes Jim 35 minutes to shovel snow from the same driveway. This means that his unit rate of working in terms of time is 1/35

If they work together, it would take a shorter time to complete the work.

This means that they would work simultaneously and their unit rates are additive.

The combined unit rates will be

1/45 + 1/35 = (35+45) / 1575

= 80/1575

Assuming that it takes a combined time of t hours to finish the work, then the combined unit rate of working will be 1/t. Therefore,

80/1575 = 1/t

t = 1575/80 = 19.6875 hours