Today’s SAT question of the day is an algebra question about rates. Get your units-per-unit brain fired up.

The question:

The c cars in a car service use a total of g gallons of gasoline per week. If each of the cars uses the same amount of gasoline, then, at this rate, which of the following represents the number of gallons used by 5 of the cars in 2 weeks?

If the total gas is g and it’s used by c cars in a week, we are using g/c gallons per car per week.

For 5 cars, we use 5(g/c) per week.  For 2 weeks, we multiply that quantity by 2:  2(5(g/c). Simplified, this is 10g/c.

Don’t jump to conclusions when working with rate problems – they seem simple (and, in fact, they are), but by working carefully and logically you can ace these each and every time.