In a $5$ -hour race, $6$ cars consumed $480$ gallons of gas between them. Assuming a constant rate of consumption, how much gas would be consumed by $7$ cars in an $8$ -hour race?

Correct answer marked below

560

654.5

768

864

896

Correct

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Comments

KrishAug 23

Thanks, this one was a nice warm-up. Once you figure out the per-car per-hour rate it basically solves itself.

DhruvJun 3

Wait, why do we divide by 5? I got 480/6 = 80 and then multiplied by 7 and 8, which gave me 4480. That's not even close to any answer.

ChrisMay 5

Sub-500 but the two-step rate conversion still trips people up. Good to see it here.

MyshaJul 26

Is there a shortcut using proportions? Like 6 cars/5 hours to 7 cars/8 hours?

What this question tests

Your ability to combine individual work rates, usually by working with the fraction of a job completed per unit of time.

Adding the times instead of the rates, or forgetting to take the reciprocal when combining rates.

In a 555-hour race, 666 cars consumed 480480480 gallons of gas between them. Assuming a constant rate of consumption, how much gas would be consumed by 777 cars in an 888-hour race?