Lesson Notes By Weeks and Term v5 - Grade 4

Lesson Video

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Performance objectives

• Identify and use standard units (cm, m, km, g, kg, ml, L).
• Read measuring instruments like rulers, scales, and jugs.
• Compare and order different measurements.
• Solve simple word problems involving measurement.

Lesson summary

Measurement is a fundamental skill that we use every day in our lives. From measuring ingredients for pap and vleis at home to understanding how far we travel on the bus, measurement helps us make sense of the world around us. In Grade 4, we will focus on three important types of measurement: length, mass, and capacity. Length helps us determine how long or tall things are. Mass tells us how heavy things are. Capacity tells us how much a container can hold. This week, we will learn about the standard units used to measure these quantities and how to estimate and measure objects accurately.

Lesson notes

Length: Length is the measurement of how long something is. We use different units to measure length depending on the size of the object.

Centimeter (cm): A centimeter is a small unit of length. Think about the width of your little finger - it's about 1 cm wide. We use centimeters to measure smaller objects, like pencils, books, and erasers. A ruler typically shows measurements in centimeters.

Meter (m): A meter is a larger unit of length. One meter is equal to 100 centimeters (1 m = 100 cm). Imagine the height of a small child; that’s approximately one meter. We use meters to measure things like the height of a door, the length of a table, or the width of a room.

Kilometer (km): A kilometer is a very large unit of length. One kilometer is equal to 1000 meters (1 km = 1000 m). We use kilometers to measure long distances, such as the distance between towns or cities, or the length of a race. Imagine the distance you would travel to visit your grandparents if they live in another town.

Example 1: A pencil is 15 cm long. A table is 2 meters long. How much longer is the table than the pencil? First, we need to convert everything to the same units. Let's convert meters to centimeters. 1 meter = 100 cm 2 meters = 2 100 cm = 200 cm Now we can compare the lengths: Table length: 200 cm Pencil length: 15 cm To find the difference, subtract the pencil length from the table length: 200 cm - 15 cm = 185 cm Answer: The table is 185 cm longer than the pencil.

Mass: Mass is the measurement of how heavy something is. We also use different units to measure mass.

Gram (g): A gram is a small unit of mass. Think about a paperclip; it weighs about 1 gram. We use grams to measure very light objects, like sweets, biscuits, and small quantities of spices.

Kilogram (kg): A kilogram is a larger unit of mass. One kilogram is equal to 1000 grams (1 kg = 1000 g). A bag of maize meal, for example, might weigh 2.5 kg. We use kilograms to measure heavier objects, like bags of potatoes, textbooks, and people's weight.

Example 2: A bag of apples weighs 2 kg. An orange weighs 200 g. Which is heavier, and by how much? First, convert kilograms to grams. 1 kg = 1000 g 2 kg = 2 1000 g = 2000 g Now we can compare: Bag of apples: 2000 g Orange: 200 g Subtract to find the difference: 2000 g - 200 g = 1800 g Answer: The bag of apples is heavier by 1800 g.

Capacity: Capacity is the measurement of how much a container can hold.

Milliliter (ml): A milliliter is a small unit of capacity. Think about an eye dropper. A few drops is about a milliliter. We use milliliters to measure small amounts of liquids, such as medicine or small amounts of juice.

Liter (L): A liter is a larger unit of capacity. One liter is equal to 1000 milliliters (1 L = 1000 ml). A carton of milk is usually 1 liter. We use liters to measure larger amounts of liquids, such as water bottles, juice cartons, and cooking oil.

Example 3: A bottle of water has a capacity of 1.5 L. A small cup has a capacity of 250 ml. How many cups can be filled from the bottle of water? First, convert liters to milliliters. 1 L = 1000 ml 1.5 L = 1.5 1000 ml = 1500 ml Now we can divide the total capacity of the bottle by the capacity of the cup: 1500 ml / 250 ml = 6 Answer: You can fill 6 cups from the bottle of water. Guided Practice (With Solutions)

Question 1: A piece of string is 35 cm long. You cut off 12 cm. How long is the string now?

Solution: Original length: 35 cm Length cut off: 12 cm Remaining length: 35 cm - 12 cm = 23 cm Answer: The string is now 23 cm long.

Commentary: This problem involves subtraction of lengths. We are using the same units (cm), so we can subtract directly.

Question 2: A bag of sugar weighs 1.5 kg. How many grams does it weigh?

Solution: 1 kg = 1000 g 1.5 kg = 1.5 1000 g = 1500 g Answer: The bag of sugar weighs 1500 g.

Commentary: This problem requires converting from kilograms to grams. We multiply the weight in kg by 1000 to get the weight in grams.

Question 3: A juice box holds 200 ml. How many juice boxes are needed to fill a 1-liter bottle?

Solution: 1 L = 1000 ml Number of juice boxes = 1000 ml / 200 ml = 5 Answer: You need 5 juice boxes to fill a 1-liter bottle.

Commentary: This problem requires converting liters to milliliters and then dividing the total volume by the individual volume.

Question 4: Mary measures the length of her desk and finds that it is 80 cm long. Sifiso measures the same desk and says it is 0.8 meters long. Are they both correct? Explain.

Solution: Yes, they are both correct. We need to convert either centimeters to meters, or meters to centimeters, to see. If we convert 80cm to meters, we divide by 100 (since 100cm = 1m), so 80cm/100 = 0.8m. Or, if we convert 0.8m to centimeters, we multiply by 100, so 0.8m x 100 = 80cm.

Commentary: This highlights the relationship between centimeters and meters. Independent Practice (Questions Only) A rope is 5 meters long. You cut it into 4 equal pieces. How long is each piece in centimeters?