<PRE><B>Question 919280</B>
lawn to be mowed is 2000 square meters.


michael can mow 1200 square meters in 8 hours.
his rate of mowing is therefore 1200 / 8 = 150 square meters per hour.


matthew can mow 600 square meters in 8 hours.
his rate of mowing is therefore = 600 / 8 = 75 square meters per hour.


mark can mow 200 square meters in 8 hours.
his rate of mowing is therefore = 200 / 8 = 25 square meters per hour.


when they work together, their rates are additive.


since rate * time = quantity, then you get:


(150 + 75 + 25) * time = 2000 square meters.


simplify by combining like terms to get:


250 * time = 2000 square meters.


divide both sides of the equation by 250 to get time = 2000 / 250 = 8 hours.


working together, they will be able to mow the the whole lawn in 8 hours.


in 5 hours, they will be able to mow 5/8 * 2000 = 1250 square meters.


looked at another way, their combined rate is 250 square meters per hour.


multiply that by 5 and you get 5 * 250 = 1250 square meters.


since the lawn is 2000 square meters and they mow 1250 square meters in 5 hours, then what is left ot mow is 750 square meters.


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