Answer: 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
