L2 · Writing equations: number = expression and expression = expression

Learning goal

“I can write an equation to match a sentence - a number equal to an expression, or one expression equal to another - and I know the two sides can swap places and still say the same thing.”

Equation — (from L1) a statement with an equal sign saying two sides have the same value.

Side — one part of an equation: the left side is everything before the equal sign, the right side is everything after it.

Expression — (from L1) numbers joined by one operation, with no equal sign.

Swap — to trade places. The two sides of an equation can swap places and the equation still says the same thing, because both sides have the same value.

Worked example

Sentence: 'Nine is the same as six plus three.' Step 1: The sentence names a plain number first: 9. Step 2: 'Is the same as' becomes the equal sign: 9 = ... Step 3: The expression goes on the other side: 9 = 6 + 3. Now swap the sides: 6 + 3 = 9. It says exactly the same thing, because both sides are worth 9. The sides of an equation are interchangeable.

Check yourself — explain it

Why do 9 = 6 + 3 and 6 + 3 = 9 say the same thing?

Paired problem — example still visible

Write the equation: 'Twenty is the same as four times five' -> 20 = 4 x 5

Faded completion — last step is yours

"'Fifteen is the same as twenty take away ___' -> 15 = 20 - ___" -> 5

Ready to practise?

10 scored questions with a 3-rung hint ladder. Mastery needs 8/10 plus both gate questions.

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