Answer: Kim can mow the greens alone in 6 hours.
Step-by-step explanation:
Let K be the rate Kim mows the greens, and S the rate for Shayla. The rates K and S will be in greens/hour.
We know they can mow 1 green in 4 hours. We can state this as a sum of their rates times the 4 hours equals one green:
(4 hours)*(K + S) = 1 green
We are told that K = 2S [Kim is twice as fast as Shayla]
Subsititute:
(4 hours)*(K + S) = 1 green
(4 hours)*(2S + S) = 1 green
4*(2S + S) = 1 green
12S = 1 green
Shalya's rate is 1 green/12 hours
Kim is twice as fast: K = 2S
Kim's rate is 1 green/6 hours.
