In 1 hour, Mary can clean 1/6 of the apartment, while her roommate cleans 1/5 of the apartment. To represent both of them working together, you add both fractions : 1/5 + 1/6 = 11/30. To find out how long it would take, you divide 1 by 11/30. 1/1 ÷ 11/30 = 1/1 × 30/11 = 30/11 hours. Make the fraction a mixed number : 30/11 = 2 8/11. 8/11 ≈ 0.727. Multiply 0.727 with 60 minutes : 0.727 × 60 = 43.62 minutes. Round 43.62 : 44 minutes. Result : 2 hours and 44 minutes.
I think boys =18 girls=12 boys :x girls:y student:z the number of group for the boys :n the numberof group for the girls :m so x=(3/5)*z y=(2/5)* z x/y=3/2 3y-2x=0 (1/10)*z*n=(3/5) *z so n=6 (1/5)*z*m=(2/5)* z put x=(1/10)*z*6 y=(1/5)*z*2 into 3y-2x=0 and z=30 z=30 so x=(1/10)*30*6=18 y=(1/5)*30*2=12
