Part 1 — Lessons (41)
1. Multiplying 2-Digit Numbers
Break the problem into parts. For 23 × 14:
- 23 × 4 = 92
- 23 × 10 = 230
- Add them: 92 + 230 = 322
Tip: Multiplying by 10 just adds a zero. Use that to check your work.
2. Finding a Percentage of a Number
What does percent mean?
'Percent' means 'out of 100'. So 25% means 25 out of every 100.
To find a percentage of a number, change the percent to a fraction over 100 and multiply. For example, 20% of 150 = (20 ÷ 100) × 150 = 30.
Quick tricks: 10% is the number divided by 10; 50% is half; 25% is a quarter.3. Equivalent Fractions
Different fractions can be equal. 1/2 = 2/4 = 3/6 — all the same amount.
Multiply (or divide) the top and bottom by the same number to find equivalents.
Example: 1/3 = (1×2)/(3×2) = 2/6.
Try this: Find a fraction equal to 2/5 with a denominator of 10. (4/10.)
4. The Mean (Average)
What is the mean?
The mean, or average, is a single number that represents a set of values.
To find it, add all the values together, then divide by how many values there are.
Example: the mean of 4, 6 and 8 is (4+6+8) ÷ 3 = 18 ÷ 3 = 6.
5. Perimeter & Area
Perimeter is the distance around a shape — add all the sides. Area is the space inside.
For a rectangle 6 cm by 4 cm: Perimeter = 6+4+6+4 = 20 cm. Area = 6 × 4 = 24 cm².
Tip: Perimeter is measured in units (cm); area in square units (cm²).