Lengths are any linear sort of measurement. You could think of it as a measurement from here to there!

Measuring distance is the process of calculating with more accuracy than estimation, how far, long, wide or tall something is.

Adding and Subtracting Lengths

Sometimes we use measurement of lengths with units when calculating the difference (which would involve subtraction) of lengths, or the total (which would involve addition) of lengths.

When adding or subtracting lengths, there is no difference to how we worked out how to add or subtract whole numbers, fractions and decimals. All of those techniques apply here - we just need to make sure we remember two things,

that lengths will always involve a unit

that we cannot add or subtract unless the units are the same or compatible (we can add like parts together).

Worked Examples

Question 1

Evaluate:$14.8$14.8 m + $203$203 cm

Think: we need a common unit, so either convert both to m or to cm.

Do: First convert $203$203 cm into m --> $2.03$2.03 m

Now complete the addition $14.8$14.8 m + $2.03$2.03 m = $16.83$16.83 m:

Or another one

question 2

Evaluate: Angelo was measuring the length of material that would be required to cover two windows. The first window measured $1$1 m $25$25 cm and the second $2$2 m $52$52 cm. What is the minimum total length of material Angelo will need to purchase?

Think: This one can be calculated without converting because the units are compatible. That is we can add the metre parts and then the centimetre parts separately, and then rejoin them together.

Do: $1$1 m + $2$2 m = $3$3 m

and $25$25 cm + $52$52 cm = $77$77 cm

So in total we have $3$3 m $77$77 cm

Angelo will need $3$3 m $77$77 cm of material.

QUESTION 3

Write down the measurement marked with an X.

QUESTION 4

I measured my height to be $1.71$1.71 metres with my shoes on. If my shoes are $4$4 cm high, what is my real height without the shoes in metres?

QUESTION 5

What is the length of the shaded bar in the image shown?

QUESTION 6

What is the angle being measured by this protractor?

$\editable{}$ degrees

QUESTION 7

The device shown is a speedometer. What is the measure indicated on it?

$\editable{}$ kilometres per hour

Outcomes

GM4-1

Use appropriate scales, devices, and metric units for length, area, volume and capacity, weight (mass), temperature, angle, and time