Question 1102077
You can mow 1 acre in 20 minutes, so your rate of mowing is 1 acre/20 mins = 1/20 acres per min
Your friend's rate is 1/25 acres per min
Working together, your combined rate is 1/20 + 1/25 = 9/100 acres/min
The time per acre is therefore 100/9 min/acre
The time to mow 12 acres is 100/9*12 = 133 1/3 min