Grade 4 › G4U09 Area & Angles

Grade 4 › G4U09 Area & Angles › L2
GRADE 4 · ALBERTAOUTCOME AB-G4-4M1

L2 · Area of a Rectangle: Side × Side (Arrays)

Learning goal

“I can find the area of a rectangle by multiplying its two side lengths, because the rectangle is an array of unit squares - and I can run the multiplication backwards to find a missing side.”

Array — units arranged in rows and columns, like the squares inside a rectangle.
Side lengths — the measurements of the two sides of a rectangle that meet at a corner (they are perpendicular to each other).
Area of a rectangle — side x side: multiply the two side lengths. The answer is in square units.
Square units — the unit written with a small 2, like cm², because area counts squares, not lengths.
Worked example

A rectangle is 6 cm long and 4 cm wide, drawn on a centimetre grid. Step 1: Tile it mentally: each row holds 6 cm squares, and there are 4 rows. Step 2: Counting all the squares gives 6 + 6 + 6 + 6 = 24. Step 3: Multiplication is the fast version of that count: Area = side x side = 6 x 4 = 24 cm². Say it plainly: the two side lengths tell you the array - how many squares in a row, and how many rows. Multiplying the sides counts every square inside, without drawing them.

Check yourself — explain it

We multiply the two side lengths because...

Paired problem — example still visible

A rectangle is 8 cm by 3 cm. Area? -> 24 cm² (8 x 3)

Faded completion — last step is yours

"A rectangle is 9 cm by 5 cm: Area = 9 x ___ = ___ cm²" -> 5; 45 cm²

Ready to practise?

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

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