7. Measurement

Lesson

Can you use an array to help solve a multiplication question?

Which of these number sentences describe the array?

There may be more than one correct answer.

A

16 \times 8 =2

B

8 \times 2 = 16

C

16 \times 2 =8

D

2 \times 8 =16

Worked Solution

Idea summary

We get the same answer whichever way we look at our array.

Let's look at how we can use arrays and multiplication to find the area, or how much space is inside, a two-dimensional (2D) shape, by counting how many unit squares fit inside it.

What is the area of the rectangle?

Worked Solution

Idea summary

We can use arrays and multiplication to find the area of a rectangle by multiplying the number of rows by the number of unit squares in each row.

In this video, we use arrays to work out the area of our rectangle but start naming the dimensions as length and width.

A square is a special kind of rectangle, so we can use the same method to work out the area. Instead of having a different number for our length and width, each side has the same length. Markers are often used, rather than write the length on every side, as this picture shows.

Find the area of the rectangle shown.

Worked Solution

Idea summary

The area of a rectangle is given by \text{Area}=\text{Length} \times \text{Width}.

When we calculate area, the unit of measurement is squared. If we have sides measured in centimetres \text{(cm)}, for example, the area will be \text{cm}^2.

Calculate the perimeter and area of rectangles and the volume and capacity of prisms using familiar metric units