# Ratio Question with 3 quantities

1. Aug 12, 2016

### zak100

1. The problem statement, all variables and given/known data
If 15 workers can pave 18 driveways in 24 days, how many days would it take 40 workers to pave 22 driveways

2. Relevant equations
Actually i dont know which equation should be used for 3 quantities. I know the eq for two quantities.
Because we increasing labours so we would require less days
Workers * days/ increased workers (i.e constant product eq)

3. The attempt at a solution

I can find days using above eq:

15 * 24/40 = 9 days
For 18 drive ways we need 9 days
For 1 drive way , we would need 18/9 = 2 days
For 22 driveways, we would need 11 days.

Is there a simple method for solving the above problem.

Zulfi.

2. Aug 12, 2016

### haruspex

Think about the work needed per driveway.

3. Aug 12, 2016

### Ray Vickson

Your method is OK in this case. In general, however, it is helpful to introduce an algebraic symbol; for example, in this case you can let $p$ be the number of driveways paved per day for 1 worker. Thus, 15 workers can pave $15p$ driveways per day, or $15 p \times 24$ driveways in 24 days.

4. Aug 13, 2016

### zak100

Hi,
Can some body guide me why the output of following is in terms of days?
15 * 24/40 = 9 days
Zulfi.

5. Aug 13, 2016

### haruspex

What are the units for the three inputs, the 15, the 24 and the 40?