7 Candy and Tim share a paper route It takes Candy 70 min to

7)

Candy and Tim share a paper route. It takes Candy 70 min to deliver all the papers, and it takes Tim 80 min. How long does it take the two when they work together?

min?

sec?

Solution

Candy\'s rate is (all the papers ) / ( 70 min )
Tim\'s rate is ( all the papers ) / ( 80 min )
Call \"all the papers\" 1 job
Add their rates to get rate working together
Let t = minute to do 1 job working together

1/70 +1/80 = 1/t

(80+70)/(80*70)=1/t

t= 80*70/150=560/15

t=37.33 min= 37 min and 20 sec

it takes them 37 min and 20 sec working together