Answer: it will take them 48 minutes.
Step-by-step explanation:
John can mow a lawn in 80 minutes. This means that the rate at which he moans the lawn per minute is 1/80
Rocky can mow the same lawn in 120 minutes. This means that the rate at which Rocky can mow the same lawn per minute is 1/120
If they work together, they would work simultaneously and their individual rates are additive. This means that their combined working rate would be
1/80 + 1/120 = 200/9600 = 1/48
Assuming it takes t hours for both of them to clean the room working together, the working rate per hour would be 1/t. Therefore,
1/48 = 1/t
t = 48 minutes
Using the place value chart we can see that the decimal 0.6 is six tenths, so we can write 0.6 as the fraction 
. Notice however that is not in lowest terms so we need to divide the numerator and the denominator by the greatest common factor of 6 and 10 which is 2.
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36.89 total divided by the 8.6 gallons he bought = 4.2 so the price per gallon would be $4.20
6 x 11= 66
67 - 66 = 1
67/6 = 11
remainder= 1
