Question 191642

Let x=amount of time it takes them to rake their dad's yard together
So, together they rake the yard at the rate of 1/x yard per min
Andrea rakes the yard at the rate of 1/45 yard per min
Then Bradford rakes at the rate of (1.5)*(1/45)=(3/2)(1/45)=3/90=1/30 yard per min
Now our equation to solve is
1/45 +1/30 = 1/x  multiply each term by 180x
4x+6x=180 collect like terms
10x=180  
x=18 min-------------------amount of time it takes them to rake their dad's yard together

CK
In 18 min Andrea can do (1/45)*18=18/45=2/5 of the lawn
In 18 min, Bradford can do (1/30)*18=18/30=3/5 of the lawn
2/5 +3/5 =5/5 (the whole lawn)

Hope this helps---ptaylor