Up Your Score (33 page)

Yes! This is the right answer. Notice that we didn’t even have to figure out what the problem was all about; we just manipulated the information so that the answer would be in the correct unit.

Let’s do another one:

A mechanic can install carburetors in 3 cars every 4 hours. At that rate, how long will it take the mechanic to install carburetors in 5 cars?

(A) 6 hrs. 20 min.

(B) 6 hrs. 40 min.

(C) 7 hrs. 15 min.

(D) 7 hrs. 30 min.

(E) 7 hrs. 45 min.

Step 1: Figure out the information given.

“3 cars every 4 hours” =

“install in 5 cars” = 5 cars

Because the answer choices are in terms of hours and minutes and because the question asks, “How long will it take?” the answer will be in terms of hours and minutes.

Step 2: Do the right thing with the information given.

Try the three options. Remember, all we care about is that the answer be in terms of the unit “hours.”

Nope. Gives answer in cars
²
/hour.

Nope. Gives answer in
. We want the hours in the numerator.

Sure enough, the third option works.

Sometimes units problems require more than one operation. For example, if you want to calculate how many seconds there are in a day, you would do the following set of operations:

Note that even if you hadn’t known that the right way to do this problem was to multiply these quantities together, you could have figured it out by trying all the possibilities of dividing and multiplying. Only one of those possibilities would have given an answer in terms of seconds/day.

Note: Don’t be tempted to bring mechanical pencils to the test. The College Board forbids them.

And now we break for a commercial . . .

Don’t you hate it when rabid elephants attack you and steal your pencils? I do. On the crucial day of my test, I was carrying no fewer than four number 2 pencils, and this tremendous elephant, foaming at the mouth, lunged out of the test center and grabbed my writing implements. I was ticked off.

But then I decided to try new improved Oxford Anti-Elephant soap. It not only cleans and softens my skin but also keeps those pesky pachyderms away. Now I can carry as many pencils with me as I like, and it’s improved my whole life.

Well, some of my life. Actually, the point of this message is to remind you to have enough number 2 pencils around when you take your test. Also, we wanted to give you a break from reading about math—after all, math is not the most exciting material available for perusal.

Now, get back to work!

You really don’t need to know much more than the basics of math to get through the word problems—but you do need to know how to think. It turns out that a lot of the math questions deal more with words than with straight math. Often the hard part is translating the words into math. You see,

looks like a hell of a problem. But it isn’t that bad because it’s just numbers and you can do it knowing only how to add, multiply, and divide. You don’t really have to think—you just have to apply the skills you’ve (supposedly) known since second grade. In fact, you could solve it on your calculator effortlessly.

The really hateful questions are the word problems:

Bill has four apples and is 18 years old. Sue has 25% more apples than Bill and is ⅓ as old. Alex had twice as many apples as Sue (and is
as old), but he gave one of his
apples to Bill (and that’s why Bill has four instead of three).

For which individual is the ratio of apples/age the greatest?

Not only do you need to know about ratios and percentage and addition, but you also need to know how to translate the words into math. (The answer is Alex, by the way.)

So let’s start with words—okay? (Put the Doritos away and pay attention.)

Following are a bunch of rules for how to change confusing words into easy-to-understand numbers and mathematical symbols.

Rule 1:
Of
usually means multiply.
For example, “½
of y
” means multiplying ½ times
y
.

Rule 2:
Exceeds by
or
is greater than by
means subtract (or add).