takes me 2 hours to mow my lawn. My son takes 2.5 hours to mow the same lawn. If we work together using two lawnmowers, how long will it take us to mow the lawn?

Answer 1

t/2 + t/2.5 = 1

Can you solve for t and answer?

Answer 2

First find the rate for each person:

Dad - 1/2

Son - 1/(2 1/2) = 1/ (5/2) = 2/5

The dad can finish 1/2 of the lawn in 1 hour and the son can finish 2/5 of the lawn in one hour, together they can finish:

1/2 + 2/5 = 5/10 + 4/10 = 9/10

Now we can set the unknown ratio to the ratio we know to determine how long it'll take them to mow the lawn, where x is the amount of time it'll take them to finish the job together:

1/x = 9/10

x = 10/9 = 1 1/9 hours ~ 1 hr 7 minutes