Question

Wendy can wash a car twice as fast as Jason. When they work together, Wendy and Jason can wash a large van in 2 hours. How many hours would it take Jason to wash the van by himself?

Answer 1

X= number of hours would it take Jason to wash the van by himself.
2x=number of hours would it take Wendy to wash the van by herserlf.

we calcaulate the fraction of  work by Jason during one hour

x hours-----------------------------1 work
1 hour----------------------   fraction of work during one hour.

fraction of work during one hour=(1 hour * 1work) / x hours=1/x


we calculate the fraction of work by Wendy during one hour.
2x hours-----------------------------1 work
1 hour----------------------   fraction of work during one hour.

fraction of work during one hour=(1 hour * 1work) / 2x hours=1/2x

We can suggest this equation:
2 hours(fraction of work by Jason during one hour + fraction of work by Wendy during one hour)=1 work

2(1/x + 1/2x)=1

least common multiple=2x
2(2+1)=2x
2(3)=2x
6=2x
x=6/2
x=3

answer: 3 hours would ti take Jason to wash the van by himself.