Today is rung 10 of 10 on this topic
Expressions, variables and what a letter means
Can do: Writes and evaluates expressions with variables, and knows a letter stands for a number, not a label.
Why it matters
The most damaging misconception in early algebra is that in 3a, a means apples. Fixing it now prevents years of confusion.
What it looks like when it's wobbly
Reads 3a as three apples; can't evaluate 2n + 5 when n = 4 without a template.
⏱️ Two-minute check
"What does 3a mean? Evaluate 2n + 5 when n = 4. Write an expression for 'a number doubled then add 7'."
Solid looks like: Three times an unknown number, 13, and 2n + 7.
The full activity for this topic · 20 minutes
The Number in the Box
- 1Put a card with a hidden number in an envelope. That envelope is n.
- 2Write expressions about it: n + 3, 2n, n ÷ 2, and say each in words.
- 3Reveal the number and evaluate every expression.
- 4Change the number and re-evaluate. The expression stayed the same — that's the power of a variable.
- 5Translate word phrases into expressions and back again.
If it's too hard
Substitution into one-operation expressions only.
If it's too easy
Expressions with brackets and exponents, and translating multi-step word descriptions.
Say this
"a isn't apples — it's a number we don't know yet. Say the expression out loud in words."