How long will it take them to mow 7 lawns

Algebra
Tutor: None Selected Time limit: 1 Day

One lawn care worker can mow 3 lawns in 60 minutes, and another worker can mow 5 lawns in 75 minutes. If they work together, how long will it take them to mow 7 lawns

Sep 10th, 2014

First find the rate for each mower,

3 lawns in 60 minutes = 20 minutes per lawn = 1/20 lawn per minute 


5 lawns in 75 minutes = 15 minutes per lawn = 1/15 lawn per minute

if they are working together to mow 7 lawns, let t = time:

(1/20)t + (1/15)t = 7

multiply through by LCD of 60:

3t + 4t = 420

7t = 420

t = 60

Both will take them 60 minutes to mow 7 lawns if they work together.

Sep 11th, 2014

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