L3 · Writing Equations with One Operation

Learning goal

“I can write an equation with one operation that tells the story of an unknown number - for adding, subtracting, multiplying, and dividing stories.”

Equation — a mathematical statement with an equals sign, claiming the left side and the right side have the same value (e.g. n + 5 = 14).

Unknown — the number in a story that we do not know yet. We hold its place with a letter (like n) or a box.

Worked example

Story: "A bag has some marbles. 5 more marbles are added. Now there are 14 marbles." Step 1: Hunt for the unknown: how many marbles were in the bag at the start? We do not know - call it n. Step 2: Follow the story in order: start with n, add 5, land on 14. Step 3: Write it with an equals sign: n + 5 = 14. One operation (+), one unknown, one equals sign. That is a Grade 4 equation. Second story, subtraction: "After giving away 8 stickers, Jen has 17 stickers left." The unknown is the starting amount: n - 8 = 17. Say it plainly: the equation is the story rewritten in symbols - same order, same operation, with a letter standing where the unknown sits.

Check yourself — explain it

In the story "some marbles, 5 added, now 14," why does n stand at the START of the equation?

Paired problem — example still visible

Write the equation for: "A number minus 6 is 13" -> n - 6 = 13

Faded completion — last step is yours

"'Some pencils, 9 more bought, now 25' in symbols: n + ___ = 25" -> 9

Ready to practise?

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

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