Grass Cutting

[Dee-M-See]

A man can mow a lawn in 30 minutes his mate can mow the same lawn in 20 minutes,how long will it take if they mow the lawn together

[Annabella72]

I think it would take 25mins (half of each man's time then add together) but it would be quicker if the 2nd guy did it in the first place! :)

[Andy Cheever]

12 minutes

1/30 + 1/20 = 1/12

[Aquariel]

I agree with Andy - in 10 mins they will have covered 5/6ths between them, therefore (10/5)*6 = 12 mins.

[Fibonacci]

I concur 12 minutes.

and herer's another way of arriving at the solution

If you assume you have a lot of identical lawns and both mowed for 1 hour.

Man 1 would mow 60/30 = 2 lawns
Man 2 would mow 60/20 = 3 lawns
So in a hour they will have together mowed 5 lawns
That's one lawn every 60/5 = 12 minutes

Now altogether one man went mow , went to mow a meadow ........