Question 26

This is a good example of a multi-step problem solving question. The question asks: how many miles per gallon did the car travel IN THE CITY? I order to determine this we would first need to know the number of gallons in the tank and then divide that number into the number of miles driven in the city (336).

Mathematical Solution

Skills Needed: Set up an equation and then solve the equation.

The problem is that we don't know the number of gallons in the tank. Hence, our first objective is to determine this number.

We are given that the number of gallons in the tank is such that the car gets 6 fewer miles per gallon in the city than on the highway. I.e. if "x" is the number of gallons:

462/x - 336/x = 6. If we were to solve for x, we would find that x = 21. In other words, the number of gallons in the tank is 21.

The number of miles in the city (336) divided by the number of gallons (21) = 16. Hence, the answer is (B).

Multiple Choice Is Our Friend Solution

But, let's do this simply by working the answer choices. We know that one of the choices must be correct. The first step is to recognize that the answer choices represent the miles per gallon traveled in the city. For an answer choice to be correct it must have the following characteristics:

First, (336/answer choice) = number of gallons in the tank.

Second, (462/number of gallons in the tank) must = answer choice + 6.

Let's start with the choice in the middle which is (C).

First, 336/21 = 16

Second, 462/16 = 28.75 (28.75 does not equal 16 + 6) 28.75 is far too big. Therefore we must divide a number greater than 16 into 462.

Let's know try choice (B).

First, 336/16 = 21.

Second, 462/21 = 22. Since, 22 - 16 = 6 (B) is correct.

Note that this process of back solving works far better for this question.