Question

Help please??

Sophie and Simon are peeling a pile of potatoes for lunch in the cafeteria. Sophie can peel all the potatoes by herself in 45 minutes, while it would take Simon 30 minutes to do the job working alone. If Sophie and Simon work together to peel the potatoes, how long will it take them?

a. 15 minutes
b. 18 minutes
c. 38 minutes
d. 75 minutes

Answer 1

b. 18

Explanation:

just did it

Answer 2

First we want to express their work in speed.

For sophie we can write:
x/45 = 1
that means that after 45 minutes (x=45) she will make 45/45 = 1 work (finish those potatoes)

for Simon we write:
x/30 = 1

Now if they work together we just need to sum their speed.

x/45 +x/30 = 1
5x/90 = 1
x = 90/5
x = 18

Answer is b) 18 minutes.