If 5 workers can pave 10 driveways in 30 days, how many days would it take 20 workers to pave 38 driveways?

Given that 5 workers can pave 10 driveways in 30 days, then:

let x be the number of days that can take 20 workers to complete 38 drive ways;

therefore:

proportion of work completed by 5 workers will be:

5*30/10

=15

proportion of work completed by 20 workers will be:

20*x/38

The time taken for 20 workers to complete 38 driveways will be:

15=20/38x

x=15*38/20

x=28 1/2

The answer is 28.5 days