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1. Basic Measurements And The Conversions Of Units. Metric conversions Units of length The basic unit of length in the metric system is meter (m). 1m = 100 cm 1 cm = 10mm 1 m = 10 dm 1 km = 1000 m Legend: m is meter cm is centimeter mm is millimeter d m is decameter km is kilometer

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3. WHY ARE SHAPES IMPORTANT? A shape is defined as a form of an object or its outline, outer boundary, or surface area. Farm lands come in different shapes.

4. Activity: Map Me Out Draw and calculate the total surface area in m2 1. For square: Length: 15 m; width 10 m 2. For rectangle: Length 15 m, width 20 m 3. For rhombus: base 10 m, height 25 m

5. CIRCLES The area or (A) of a circle is calculated by the formula: Or 𝐴 = 𝜋𝑟 Whereby d is the diameter of the circle and 𝜋 (a Greek letter, pronounced pi) a constant ( 𝜋 = 3.14). A diameter (d) is a straight line which divides the circle in two equal parts.

6. SURFACE AREAS OF CANAL CROSS-SECTIONS AND FARMS The "up- sidedown " trapezium is the most common shape of a canal cross-section. Canal cross section

7. The area (A B C D), hatched on the above drawing, is called the canal cross-section and has a trapezium shape. Thus, the formula to calculate its surface is similar to the formula used to calculate the surface area of a trapezium: Or: A = ½ (a+b) x h Whereby: Base (b) = bottom width of the canal Top line (a) = top width of the canal Canal depth (h) = height of the canal (from the bottom of the canal to the top of the embankment)

8. Wetted cross-section of a canal The area (A B C D), hatched on the above drawing, is called the wetted canal cross-section or wetted cross-section. It also has a trapezium shape. The formula to calculate its surface area is: Whereby: Base (b) = bottom width of the canal Top line (a1) = top width of the water level Water depth (h1) = the height or depth of the water in the canal (from the bottom of the canal to the water level).

9. EXAMPLE Calculate the surface area of the cross-section and the wetted cross section.

10. Field of regular shape Example: Given: Length of the field =50 m Width of the field = 30 m

11. Question: What is the area of the same field, in hectares? Answer: A hectare is equal to 10 000 m. Thus, the formula to calculate a surface area in hectares is: Surface area in hectares (ha) = 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑖𝑛 𝑠𝑞𝑢𝑎𝑟𝑒 𝑚𝑒𝑡𝑒𝑟𝑠 ( 𝑚 2) 10,000

12. Dividing an irregular field into regular area Question: How to compute the area of square, rectangle, triangle and the total area of the field?

13. Percentage The word "percentage" means literally "per hundred"; in other words one percent is the one hundredth part of the total. You can either write percent, or %, or 1/100, or 0.01.

14. How to convert a percentage to a decimal: Remove the percentage sign and divide by 100 15.6 % becomes 15.6/100 = 0.156 How to convert a decimal to a percentage: Multiply by 100 and append a percentage sign 0.156 becomes 0.156 * 100 = 15.6% Examples : How many oranges is 1% of 300 oranges? So convert 1% to decimal by simply dividing 1% by 100 1 % = 100 0.01 then multiply it by 300, it will give you 3. So 1% of 300 oranges is 3 oranges.