Working together, Greg and Cindy can clean the snow from the driveway in 12 minutes. It would have taken Cindy, working alone, 28 minutes. How long would it have taken Greg alone?

Greg alone will clean the snow in 21 minutes

Explanation:

From the question, Greg + Cindy can clean the snow in 12 minutes

Cindy working alone is able to clear the same quantity of snow in about 28 minutes.

Now, Greg + Cindy 12

Cindy alone 28

we'll simply reduce 28/12 to its lowest term and we should have 7/3

It's very logical that two people can execute a task in less time than just one person as long as all are working at the same rate and in the same conditions.

Let's now take 7 joules as the sum of Greg and Cindy's energy and 3 joules as the quantity of Cindy's energy alone. Greg's supposed quantity of energy should be - (7-3 = 4 joules).

Therefore, Greg's + Cindy's energy/ 7joules of energy can be used to execute a task in 12 minutes. Greg's energy alone/ 4joules of energy can execute a task in ? minutes

7 joules 12 minutes

4 joules ? minutes

= 7/4 × 12 = 21 minutes

This means that Greg is able to clean the snow in 21 minutes