Your gentle introduction to algebraic thinking - no prior experience needed!
Algebra is the study of patterns and relationships. Instead of working with specific numbers, we use letters and symbols to represent general situations.
If apples cost $2 each, how much for x apples?
Cost = 2 × x
Each week a plant grows 3 inches. After w weeks?
Height = 3 × w
Convert Celsius to Fahrenheit: multiply by 9/5 and add 32
°F = \frac{9}{5} × °C + 32
Look at these numbers: 2, 4, 6, 8, ?
What comes next?
Pattern: Add 2 each time
Algebraically: Each number is 2 times its position
n^{th} number = 2n
Counting numbers: 1, 2, 3, 4, ...
Natural numbers plus zero: 0, 1, 2, 3, ...
Whole numbers and negatives: ..., -2, -1, 0, 1, 2, ...
Fractions and decimals: 1/2, 0.5, 3.14, ...
8 + 5 =
12 - 7 =
6 × 4 =
20 ÷ 5 =
When dividing fractions, remember: \frac{a}{b} \div \frac{c}{d} = \frac{a}{b} \times \frac{d}{c}
Solve: \frac{1}{2} \div \frac{1}{4} = \, ?
Multiply by the reciprocal: \frac{1}{2} \times \frac{4}{1}
Multiply numerators and denominators: \frac{1 \times 4}{2 \times 1} = \frac{4}{2}
Simplify: \frac{4}{2} = 2
Visual: One half divided by one quarter = 2
Variables are letters that represent unknown or changing values. Think of them as empty boxes waiting to be filled with numbers.
If you have some number and add 3, you get 8.
What is the number? We can write: x + 3 = 8
Here, x is the unknown number we're trying to find.
You have some apples. You give away 2 apples and have 5 left.
How many did you start with?
You buy candy for $3 and have $2 left from $10.
How much did the candy cost? (Wait, that's not right...)
The goal is to get the variable alone on one side of the equation. Whatever you do to one side, you must do to the other side.
Solve: x + 5 = 12
x =
Solve: y - 3 = 9
y =
Solve: 2z = 16
z =
Word problems can seem tricky, but they're just stories that need to be turned into equations.
Problem 1: Sarah has some stickers. She gives 4 to her friend and has 9 left. How many did she start with?
Equation: x - 4 = 9
x =
Problem 2: A movie ticket costs $8. You have $20. How much change will you get?
Equation: 20 - 8 = x
x =
Before moving on, make sure you understand: