Albert can weed a garden in 4 hours. Biddy takes 6 hours. If they decide to work together,assuming they maintain the same rates, calculate the fraction of the garden they can weed in 1 hour

Question

ZIMSEC NOVEMBER 2013 QUESTION 2c

Answer 1

Albert can weed 1/4 garden in 1 hour while Biddy can weed 1/6 garden in an hour. Together they can weed 1/4+1/6=3/12+2/12=5/12 of a garden in an hour.

Another way to do this is to suppose there are 12 weeds in the garden. If it takes 4 hours to remove 12 weeds, Albert must remove 12/4=3 weeds in an hour; and Biddy could only remove 2 (12/6=2) an hour. So in an hour they could only together remove 5 weeds, which is 5/12 of the weeds in the garden.