ISEE Lower Level Quantitative Reasoning

The ISEE Lower Level Quantitative Reasoning subject focuses on developing mathematical reasoning skills through problem-solving and critical thinking.

Advanced Topics

Using Variables and Simple Equations

Introducing Variables

Variables are symbols, like \( x \) or \( y \), that stand for a number you don’t know yet. They help you write equations to solve problems.

What is an Equation?

An equation is like a balance: both sides must be equal. For example, \( x + 3 = 7 \).

Solving Simple Equations

To find the value of a variable, do the same thing to both sides until the variable is alone.

Why Use Variables?

Variables make it easier to solve puzzles and represent real-life situations, whether you’re figuring out how many apples you need or the number of minutes left in a game.

Everyday Examples

If you know the total and one part, you can use a variable to find the missing piece.

Key Formula

\[x + 3 = 7\]

Examples

  • If \( x + 5 = 12 \), then \( x = 7 \).

  • If you have \( n \) candies and you eat 3, you have \( n - 3 \) left.

In a Nutshell

Variables and equations help you solve for unknowns in math and life.

Key Terms

Variable
A letter or symbol that stands for a number.
Equation
A math sentence showing two sides are equal.