This is a centimetre ruler. The abbreviation for centimetre is **cm**.

Measure from **0 **mark on the ruler. The pencil is according to this ruler 4.5 cm in length. It may be necessary to approximate the measurement of the items to the nearest whole number. Thus, this pencil is approximately 5 cm in length.

Note: Use your understanding of fractions to help you understand the number 4.5. Above, every 10 strokes represent one centimetre. Half way is 5 strokes or ^{5}/_{10} which is also 0.5.

### MEASURING DISTANCE

The video below will help you understand how to use a ruler to measure things.

### ACTIVITY 1

Gather the following items and measure them with your ruler. Do this activity with a parent or in class!

- ruler
- note book
- eraser
- spoon
- comb
- hairbrush
- dollar coin
- spoon
- small toy car
- glue stick

You can also find familiar items around you that you can measure. Enjoy the activity!

### ACTIVITY 2

Draw some lines that measure various lengths, such as: 6 cm, 4 cm, 9 cm.

### ACTIVITY 3

Measure the following in your classroom: the desk, black board, the width of the doorway, the bookshelf, drawers, teacher’s desk, and the length and width of your classroom.

### ACTIVITY 4

Take a walk around the neighbourhood and check the distance traveled. For instance, note the distance between your home to the nearby grocery store, or to school, or church, or to grandmother, or your friend.

These activities are important. Do them! Then proceed to the exercises.

## ADDITION OF LENGTHS

You compute various lengths by using the relationship between the metre and the centimetre, or kilometre and metre, etc.

**Let’s look at another example:**

A builder has two lengths of planks. What is the combined length of the two lengths of planks?

Add the two parts. Thus: 14 m + 9 m = **23 m** (Answer)

**Example 3:**

The length of two roads are 5km 58 m and 4 km 65 m. Calculate the total length of the two roads.

Note: The above answer 10 km 230 m can also be written as 10.23 km. This is because 230/1000 is the same as 0.23 km.

PAGE BREAK

### SUBTRACTION OF LENGTHS

Examples:

Jamie traveled 15 km. Solange traveled 6 km and 41 m? Calculate the difference.

Answer is 8km 959

Note: The answer can also be 8.959 km. Above 959/1000 km is also 0.959 km.

PAGE BREAK

### MULTIPLICATION OF LENGTHS

**Example 1:**

A runner ran a distance of 500 m on Monday. If he ran the same distance on Tuesday, Wednesday, and Thursday, what was the total distance he ran on all the days?

The runner ran 500 m x 4 = 2000 m

**Example 2:**

A piece of wire measures 5 m and 45 cm in length. 4 lengths of the wire is needed. How much lengths of wire is there in all?

PAGE BREAK

### DIVISION OF LENGTHS

Remember, first convert to the smallest measure to have one number then divide. Then, express the value as before.

**Example**: My dad is cutting a length of wire into 5 pieces. How long will each length be if the wire he cuts is 8 m and 25 cm long.

PAGE BREAK

### PERIMETER

The word perimeter refers to distance around a shape. Thus if you are asked to find the perimeter of a soccer field, you must measure the distance around the field. Say you know that the soccer field has the following distances.

To find the total distance around the field you add the four sides of the field.

Thus: 120 + 90 + 120 + 90 = 420 m total distance or perimeter of the soccer field.

PAGE BREAK

## PROBLEM SOLVING

Let’s look at two questions for Problem solving.

What you should note when you are working out problems:

- Work the problem in steps.
- Show your steps and write short statements.
- Check your workings.
- Consider, sometimes you may have to convert before you work your questions.

### QUESTION:

- Mr. Zimmern needs 8 pieces of steel of equal lengths to build a gate. If 1 length of steel is 6 m 45 cm, what is the total length of steel needed to build the gate?
- If he pays $30 for a metre of steel, how much would he pay for the total length of steel needed?

### ANSWERS:

- Total length needed for the gate is
**51 m 60 cm**= 51.6 m - Cost of steel = $30 x 51 m 60 cm = 30 x 51.6 =
**$1548.00**