SOLUTION: sam can mow the lawn in 20 min. bob can mow the lawn in 30 min. if they work together, how long will it take to completely mow the lawn.

Question 83272This question is from textbook introductory algebra
: sam can mow the lawn in 20 min. bob can mow the lawn in 30 min. if they work together, how long will it take to completely mow the lawn. This question is from textbook introductory algebra

Answer by Kalmetam(43) (Show Source): You can put this solution on YOUR website!
If sam can mow the lawn in twenty minutes, he can mow 100% in 20 minutes. So, 1 minute is 5%. Bob can mow 100% in 30 min but... 30 can't go into 100 evenly so we have to make it a percentage of something divisble by 30 and 20 in the hundreds so you can do the 300s. Since 30 min is 300%, 1 minute is 10%. Since we changed the 1st one too... it is 300% in 20 minutes and so 1 minute is equal to 15% because 300/20=15. Together, in 1 minute, they should finish 10% + 15% which is 25% and 25% can go into 300% evenly. It can go into it 12 times. So the answer is 12 minutes.
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