SOLUTION: Suppose Karen can weed the garden twice as fast as Crilyn. Together they can weed the garden in 3 hours. How long would it take each of them working alone?

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Question 1173562: Suppose Karen can weed the garden twice as fast as Crilyn. Together they can
weed the garden in 3 hours. How long would it take each of them working alone?
Found 2 solutions by ikleyn, josgarithmetic:
Answer by ikleyn(52798) About Me  (Show Source):
You can put this solution on YOUR website!
.
Suppose Karen can weed the garden twice as fast as Crilyn. Together they can
weed the garden in 3 hours.
How long would it take each of them working alone?
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Karen alone works as two instances of Crilyn.


So, they both work as three instances of Crilyn and make the job in 3 hours.


It means that Crilyn, working alone, will complete the entire job in 3*3 = 9 hours.


Karen, working alone, will make it twice as fast, i.e. in  9/2 = 4.5 hours.

Solved.

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It is the way to solve the problem  MENTALLY,  without using  ANY  equations.



Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
Karen's rate, 2%2Fc
Crilyn's rate, 1%2Fc
The two together, 1%2F3

2%2Fc%2B1%2Fc=1%2F3
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3%2Fc=1%2F3
c%2F3=3
c=9
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9 hours just for Crilyn
4.5 hours just for Karen