5th Grade algebra · Ages 10–11
Undo It
Grade 5 is where children learn the one move that solves almost everything: do the opposite, to both sides.
The one idea
To find a hidden number, undo what was done to it — with the opposite operation, on both sides.
Ready?
5th Grade algebra · Undo It
Grade 5 is where children learn the one move that solves almost everything: do the opposite, to both sides.
Full screen — no distractions
For grown-ups: 5th Grade algebra
x is just this year’s name for the box. The new skill is solving x + 9 = 23 by undoing, rather than by guessing. Guessing works for small numbers and fails later, so praise the undoing even when guessing would have been faster.
This page is the right one if they can already…
- Evaluates expressions like 3n + 2
- Knows the order of operations
- Knows multiplication and division facts to 10 × 10
Not yet? Start at 4th Grade: Number Recipes — algebra only works one rung at a time.
🏠 Try it at home
Opposites undo each other
Put on socks, then shoes. To undo: shoes off first, then socks. Undoing goes in reverse — and uses the opposite move.
Solve one-step equations
Use the interactive scale below on the hardest setting. Can they get the box alone in the fewest moves?
2x means 2 times x
Pocket money: “You get 2x + 5 dollars, where x is the number of chores.” What do 3 chores earn?
Rules make pictures
Play battleships on squared paper using (across, up) coordinates.
The words, in plain English
- x
- The most common letter for an unknown.
- x + 9 = 23
- Inverse operation
- The move that undoes another.
- ÷ 6 undoes × 6.
- Solve
- Find the number that makes the equation true.
- x + 9 = 23, so x = 14.
- Coefficient
- The number stuck to a letter.
- In 6x, the coefficient is 6.
- Coordinates
- A pair (across, up) giving a point’s place.
- (3, 6)
🌍 Algebra in an ordinary day
- “The bill was $42 split between 6 people — how much each?”
- Working out how many weeks of saving $5 gets you to $35
- Reading a map grid: B4, then coordinates
🏁 By the end of 5th Grade
- Names the inverse of each operation
- Solves one-step equations by undoing, on both sides
- Evaluates expressions with coefficients like 2x + 5
- Plots points from a rule and sees the line
Where this fits
One idea, twelve rungs. The hiding spot just gets cleverer.
Frequently Asked Questions
What algebra should a 5th Grade child learn?
To find a hidden number, undo what was done to it — with the opposite operation, on both sides. By the end of the year they should be able to: names the inverse of each operation; solves one-step equations by undoing, on both sides; evaluates expressions with coefficients like 2x + 5; plots points from a rule and sees the line.
Isn’t 5th Grade too early for algebra?
No — undo it is standard 5th Grade maths in most curricula. This page breaks it into single moves so it never feels like a jump.
What is the most common 5th Grade algebra mistake?
Solves x + 9 = 23 as x = 32. They do the same operation again instead of the opposite one. The fix: Ask before calculating: should x be bigger or smaller than 23? x plus something is 23, so x must be smaller.
What if my child is stuck?
Go down one rung. Every lesson here builds on the 4th Grade page, and the “ready for this page if” list at the top tells you exactly what they need first. In practice, a wrong answer gives a hint, and a second wrong answer shows the full worked solution.
Is it free?
Yes. All 4 lessons, the pictures, the worked examples, the balance scale and the practice questions are free with no signup. The practice never runs out — every question is generated fresh and checked.