Question

The number of race cars that can be produced varies directly with the number of people working on their production and the time taken to produce them. If 20 race cars can be produced in 40 hours with 2 people working on their production, how many race cars can be produced in 12 hours with 3 people working on their production? any help? i don't need the answer just the steps.

Answer 1

no of race cars be r and no of people producing it be p and time taken be t.
40t=>2p=>20r
assume that each one has equal capacity to built a car
so 80t=>1p=>20r( as 1 person will take twice the time without his partner to built same no of cars as we assume above)
1t=>1p=>r/4(assuming equal no of cars built in unit time)
so
12t=>1p=>3r
12t=>3p=>9r

Answer 2

@lydiagrace You can work the problem out using man x hours, wich measures capacity. So 40 hours 2 people gives 80 men·hours for 20 cars. That means that for each car you need 4 men·hours.
If you have 3 people working 12 hours, now you have a capacity of 36 men·hours. If each car needs 4 men·hours, how many cars you can produce?