Let's assign a "nice" value to the job of shoveling a driveway.
We want a value that works well with the given information: 12 minutes and 36 minutes.

So, let's say the job of shoveling a driveway consists of removing 36 cubic feet of snow.

Michael can shovel all the snow off a standard driveway in 12 minutes
In other words, Michael can shovel 36 cubic feet of snow in 12 minutes
So, Michael's RATE = 3 cubic feet per minute

Eamon can shovel all the snow off a standard driveway in 36 minutes
In other words, Eamon can shovel 36 cubic feet of snow in 36 minutes
So, Eamon's RATE = 1 cubic foot per minute

Working together, how many minutes would it take for them both to shovel all the snow off a standard driveway?
Their combined RATE = 3 + 1
= 4 cubic feet per minute

Time = output/rate
So, time to complete job = 36/4 = 9 minutes

Answer: 9

Cheers,
Brent

If a person can finish a job in \(X\) minutes, while another person can finish the same job in \(Y\) minutes, then they can finish the job working together in \(\frac{XY}{(X + Y)}\)

\(= \frac{(12)(36)}{(12 + 36)} = \frac{(12)(36)}{48} = 9\) minutes

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