Question

Working alone, it would take Shandra 45 minutes to mow the lawn. To mow the same lawn, also working alone, it would take Kelly 1 hour and 15 minutes. If they work together, the girls believe it will take them 1 hour to mow the lawn.
Which best describes the reasonableness of their solution?

Answer 1

You could add the time it takes them individually together and divide by 2. That would give you the average, which is 1 hour.

Answer 2

Answer:

While working together, they will complete the work in 28.125 minutes

Step-by-step explanation:

Working alone, it would take Shandra 45 minutes to mow the lawn.

Working alone, it would take Kelly 1 hour and 15 minutes. to mow the lawn. In minutes this becomes $60+15=75$ minutes.

So, when they are working together, they will complete 1 job.

Lets the time taken by both working together be t

Equation forms:

$\frac{t}{45} +\frac{t}{75} =1$

=> $\frac{5t+3t}{225} =1$

=> $\frac{8t}{225} =1$

=> $8t=225$

t = 28.125 minutes

Hence, while working together, they will complete the work in 28.125 minutes which is very less than their estimation.