Measurement Notes, Quizzes & Revision

What is measurement?

Measurement is a way to find the size, amount or capacity of things using agreed units and tools. In Kenya (and most of the world) we use the metric system: millimetres, centimetres, metres, kilometres for length; grams and kilograms for mass; millilitres and litres for capacity; degrees Celsius for temperature; seconds, minutes and hours for time.

Common units and tools

• Length: mm, cm, m, km — tools: ruler, metre rule, tape measure.
• Mass (weight): g, kg, tonne — tools: kitchen scale, beam or digital scale.
• Capacity (volume of liquids): mL, L — tools: measuring cylinder, jerrycan (commonly 20 L), water container, litre bottle.
• Time: seconds, minutes, hours — tools: clock, stopwatch, phone.
• Temperature: °C — tool: thermometer.
• Special: mm for rainfall (rain gauge), km for road distances (odometer or map).

Measuring length — quick tips

Use the largest suitable unit to keep numbers reasonable (e.g., use metres for classroom length, centimetres for the height of a book). Always read from the zero mark on the ruler or tape. Start measuring from one end and keep the tool straight.

Conversions (metric)

Useful conversion facts:

• 10 mm = 1 cm
• 100 cm = 1 m
• 1 000 m = 1 km
• 1 000 g = 1 kg
• 1 000 mL = 1 L

To convert: multiply or divide by powers of 10. Example: 3.5 m = 350 cm (×100).

Perimeter, area and volume — simple formulas

• Perimeter of a rectangle: P = 2(length + width). Example: classroom 8 m by 6 m → P = 2(8 + 6) = 28 m.
• Area of a rectangle: A = length × width. Same classroom → A = 8 × 6 = 48 m².
• Volume of a cuboid (box): V = length × width × height. A water tank 2 m × 1.5 m × 1 m → V = 3 m³ = 3 000 L (1 m³ = 1 000 L).
• Area of a triangle: A = 1/2 × base × height.

Accuracy, estimation and reading scales

- Accuracy: how close a measurement is to the true value. Use the correct tool (e.g., tape for a room, ruler for a book).
- Precision: how detailed a measurement is (mm vs cm).
- Estimation: a quick, sensible guess — useful when exact tools are not available (e.g., estimate litres of water in a jerrycan).

Reading a scale: line up the pointer with markings; if between marks give the nearest fraction (e.g., 1.5 kg).

Practical Kenyan contexts and examples

• Maize sack weight: sacks often sold as 2 kg, 10 kg, 50 kg, or 90 kg (check local pack). Use a scale to check weight before sale.
• Jerrican capacity: common jerrican = 20 L. Two jerricans = 40 L.
• Rainfall: measured in mm using a rain gauge. Farmers use mm to decide planting and irrigation.
• Road distances: given in kilometres (km) — use km for long distances between towns, metres for shorter local distances.
• Classroom measures: measure desks, chalkboard and arrange furniture using metres and centimetres for comfort and safety.

Practice exercises (with short solutions)

1. Measure a classroom wall and record: 7.5 m by 3.2 m. Find the perimeter and area.
   Answer: P = 2(7.5 + 3.2) = 21.4 m. Area = 7.5 × 3.2 = 24.0 m².
2. Convert 2.75 m to centimetres.
   Answer: 2.75 × 100 = 275 cm.
3. A jerrican holds 20 L. How many jerricans to carry 150 L of water?
   Answer: 150 ÷ 20 = 7.5 → 8 jerricans (need part of the 8th).
4. A farmer measures a box: 0.6 m × 0.3 m × 0.4 m. Find its volume in litres.
   Answer: V = 0.6×0.3×0.4 = 0.072 m³ = 72 L (since 1 m³ = 1 000 L).

Tips for learners and teachers (Kenyan classrooms)

• Always write units with numbers (e.g., 5 m, not just 5).
• Practice measuring real objects: desks, blackboard width, a sachet of milk, a jerrican of water.
• Use local examples (market scales, maize sacks) to make measurement meaningful.
• Encourage checking work: measure twice, record once.