# Solving One-Step Equations on the ISEE

#### All Levels

**ISEE Question:** When a number is tripled, the result is fifteen. What is twice the number?

(A) 3

(B) 5

(C) 7

(D) 10

**Solution:** Let’s focus on the only two “mathematical” words in the first sentence: “**tripled**” and “**fifteen**.”

STEP 1: To translate the sentence into a mathematical equation, we can use “b” as for the unknown variable (“**a number**,” the problem calls it), and remember that “**is**” means “=”. Our equation will read “**3b = 15**”.

STEP 2: Now, you probably already figured out that 3 x 5 = 15 and, therefore, our number b = 5. But if the equation were a bit more complicated, say “7b = 12”, then you’d have to isolate the b by dividing by 7 on both sides. The result will be

STEP 3: If you already picked B), you fell into one of the most common ISEE traps: picking the correct answer to the question you *thought* you were given and not to the question you were *actually* given. In this case, we are looking for “**twice the number**,” so the answer is 5 x 2 = 10, or D).

**Helpful Tip:** Always circle what the question is asking for when you first read it (in this case, the words “twice the number”) and have a look at that again before you bubble in your answer choice.