Area and Land Measurements
Primary 4 · Mathematics
Area and Land Measurements
Lesson 5 of 5
20 min
Let's begin
In Mugisha's village, families grow maize together on big shared fields. His family farms 1 ha 60 a. His uncle farms 85 a.
How much land do they farm together? How much more does Mugisha's family farm? Today you will add, subtract and solve land problems.
Worked example 1
A plot is 40 m long and 25 m wide. What is its area in ares?
Step 1 Area = 40 × 25 = 1 000 m².
Step 2 1 000 ÷ 100 = 10 a.
Worked example 2
A field is 200 m long and 150 m wide. Area = 200 × 150 = 30 000 m². 30 000 ÷ 10 000 = 3 ha.
Worked example 3
1 ha 60 a + 85 a
Step 1 Add the ares: 60 + 85 = 145 a.
Step 2 145 a = 1 ha 45 a. Keep 45 a and carry 1 ha.
Step 3 Add the hectares: 1 + 1 = 2 ha.
Together they farm 2 ha 45 a.
Worked example 4
3 ha 20 a − 1 ha 75 a
Step 1 20 a take away 75 a? Not enough! Break 1 ha into 100 a. Now there are 100 + 20 = 120 a, and 2 ha.
Step 2 120 − 75 = 45 a.
Step 3 2 − 1 = 1 ha. The answer is 1 ha 45 a.
Worked example 5
A cooperative has a 5 ha field. It plants beans on 2 ha 30 a and maize on the rest. How much land has maize?
In ares: 500 a − 230 a = 270 a = 2 ha 70 a.
Worked example 6
A farmer rents a plot 30 m long and 20 m wide. The rent is 2 000 Frw for each are, for one season. How much is the rent?
Step 1 Area = 30 × 20 = 600 m² = 6 a.
Step 2 Rent = 6 × 2 000 = 12 000 Frw.
Careful! With land units, you carry and borrow 100, not 10 and not 1 000.
Tip
100 ares make a hectare. When the ares reach 100, carry 1 ha. When there are too few ares, break 1 ha into 100 a.
Work each one in your exercise book first. Then tap Show answer to check.
A plot is 50 m long and 20 m wide. What is its area in m² and in ares?
Answer: 1 000 m², which is 10 a.
2 ha 70 a + 1 ha 50 a
Answer: 4 ha 20 a. 70 + 50 = 120 a = 1 ha 20 a. Then 2 + 1 + 1 = 4 ha.
4 ha 10 a − 1 ha 60 a
Answer: 2 ha 50 a. Break 1 ha: 110 − 60 = 50 a. Then 3 − 1 = 2 ha.
A farm of 3 ha is shared equally between 4 children. How many ares does each child get?
Answer: 75 a. 3 ha = 300 a, and 300 ÷ 4 = 75.
A square field has sides of 100 m. What is its area in hectares?
Answer: 1 ha. 100 × 100 = 10 000 m² = 1 ha.
What you learned today
Sources and credits
The land units, stories, Rwandan examples and practice questions were written by Ganzaa.
Quick check
A plot is 30 m long and 10 m wide. What is its area in ares?
