Word Problems
One of the Evil Testing Serpent’s favorite activities is to disguise algebra
problems within word problems.
A phone company charges $4 for the first 3 minutes of an international
call, then $.50 per minute thereafter. Which of the following represents
the total charge, in dollars, for an international call lasting x minutes?
A) x (4 + .5)
B) .5x + 4
C) 4 (x + 3) + .5
D) .5 (x – 3) + 4
There are two ways to do this problem, translating and plugging in. To
translate, we try to convert the language of the problem into an equation. Here,
we see that after the first three minutes, we start to multiply each minute by $.50.
So (x – 3) × .50 will find us the amount we are charged after those three minutes.
To account for those first three minutes, we just add the four dollars (+4). So our
final equation is .5 (x – 3) + 4, or D.
For some people, this is a fine way to solve the problem. If you are one of
those people, more power to you. But here at Up Your Score, we find it much
easier (and less open to stupid errors) to plug in.* Let’s say, for example, that our
call is seven minutes. The first three minutes cost us $4, then there are four