Lesson Notes By Weeks and Term v5 - Grade 4

Lesson Video

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Performance objectives

• Measure and record length in metres (m) and centimetres (cm).
• Measure and record mass in kilograms (kg) and grams (g).
• Measure and record capacity in litres (L) and millilitres (mL).
• Solve simple word problems with measurement.

Lesson summary

Measurement is a crucial part of our everyday lives. In South Africa, we use measurements constantly, from buying groceries at the local spaza shop to calculating distances for a trip to Kruger National Park. Understanding length, mass, and capacity helps us make informed decisions, solve problems, and appreciate the world around us. Without measurement, we couldn't build houses, cook meals, or even play sports effectively! Imagine trying to share a cool drink equally amongst your friends on a hot day without understanding capacity!

Lesson notes

2.1 Length Length refers to how long something is. We commonly use metres (m) and centimetres (cm) to measure length. A metre is a bigger unit than a centimetre. 1 metre (m) = 100 centimetres (cm) Imagine measuring the length of your classroom chalkboard. You could use a metre stick, which is 1 metre long. If the chalkboard is longer than the metre stick, you would need to measure it several times and add up the measurements. You can also use a measuring tape, which often has both centimetres and metres marked on it.

Example 1: Let's say you want to measure the length of your textbook. You use a ruler, and it measures 25 cm. The length of your textbook is 25 cm.

Example 2: You want to measure the height of the door in your classroom. You use a metre stick and find that it's 2 metres tall. Then, you notice that the door is a bit taller than 2 metres. Using a ruler, you measure the extra part and find that it's 10 cm. So, the total height of the door is 2 metres and 10 centimetres, which can be written as 2 m 10 cm or 210 cm.

Important Tip: Always remember to include the units (cm or m) when writing your measurements. 2.2 Mass Mass is how heavy something is. We use kilograms (kg) and grams (g) to measure mass. A kilogram is a bigger unit than a gram. 1 kilogram (kg) = 1000 grams (g) Think about weighing a bag of potatoes you bought at the market. It is likely weighed in kilograms. Or consider weighing a handful of sweets; it will be more appropriate to measure them in grams.

Example 1: You want to weigh a bag of oranges. You use a kitchen scale and it shows 2 kg. The mass of the oranges is 2 kg.

Example 2: You have a small packet of salt. You weigh it on a kitchen scale and it shows 500 g. So, the mass of the salt is 500 grams. What if you want to know what half a kilogram (kg) is in grams (g)? Since 1 kg is equal to 1000 g, half a kilogram would be 1000 g / 2 = 500 g.

Important Tip: When using a scale, make sure it is placed on a flat, stable surface to get an accurate measurement. 2.3 Capacity Capacity is how much a container can hold. We use litres (L) and millilitres (mL) to measure capacity. A litre is a bigger unit than a millilitre. 1 litre (L) = 1000 millilitres (mL) Imagine a 2-litre bottle of cool drink. That's a measure of its capacity. Or a small medicine spoon, which might hold only 5 millilitres.

Example 1: You want to measure how much water a bottle can hold. You use a measuring jug and find that it can hold 1 L of water. The capacity of the bottle is 1

L. Example 2: You want to measure how much juice is in a small juice box. You pour it into a measuring cup and find it holds 250 mL. So, the capacity of the juice box is 250 mL. What if you want to know how many 250mL juice boxes you need to get 1 litre of juice? Since 1 L is equal to 1000 mL, you would need 1000 mL / 250 mL = 4 juice boxes.

Important Tip: When measuring liquids, ensure your eyes are level with the surface of the liquid to get an accurate reading. Guided Practice (With Solutions)

Question 1: A table is 150 cm long. How long is it in metres and centimetres?

Solution: We know that 100 cm = 1 m. The table is 150 cm long, which is more than 100 cm (1 m). We can split 150 cm into 100 cm + 50 cm. 100 cm = 1 m, so 150 cm = 1 m 50 cm.

Answer: The table is 1 m 50 cm long.

Question 2: A bag of apples weighs 1.5 kg. How much does it weigh in grams?

Solution: We know that 1 kg = 1000 g. The bag of apples weighs 1.5 kg. This is the same as 1 and a half kilograms. 1 kg = 1000 g 0.5 kg (half a kg) = 1000 g / 2 = 500 g Therefore, 1.5 kg = 1000 g + 500 g = 1500 g Answer: The bag of apples weighs 1500 g.

Question 3: A jug contains 500 mL of juice. How many jugs of juice are needed to have 2 litres of juice?

Solution: We know that 1 L = 1000 mL. We want to have 2 litres, so we need 2 1000 mL = 2000 mL. Each jug contains 500 mL. To find out how many jugs we need, we divide the total amount needed (2000 mL) by the amount in each jug (500 mL): 2000 mL / 500 mL = 4 jugs.

Answer: You need 4 jugs of juice.

Question 4: Thando measured a piece of string and found it was 85 cm long. Lerato measured another piece of string and found it was 1 m 10 cm long. What is the total length of the two strings in centimetres?

Solution: We need to express both lengths in the same units, which is centimetres in this case. Thando's string is 85 cm long. Lerato's string is 1 m 10 cm long. We know 1 m = 100 cm. So, Lerato's string is 100 cm + 10 cm = 110 cm long.

Now we can add the two lengths: 85 cm + 110 cm = 195 cm Answer: The total length of the two strings is 195 cm. Independent Practice (Questions Only) A fence is made up of 5 sections, each 2 metres long. What is the total length of the fence in metres? A recipe calls for 250 g of flour, 100 g of sugar, and 50 g of butter. What is the total mass of these ingredients in grams? A bucket contains 3 litres of water. You use 800 mL of the water to wash your hands. How much water is left in the bucket in millilitres?