DepEd MELC reviewer for Grade 9 Mathematics, Quarter 3. Study the rules, worked formulas, and exam hacks below.
1
Similarity and Proportion
Similar figures have equal angles and proportional sides. Use ratios to find missing lengths.
💡 Exam Hack
Set up a proportion: corresponding sides form equal ratios. Cross-multiply to solve.
2
Parallelograms
| Property | Parallelogram |
|---|---|
| Opposite sides | Equal and parallel |
| Opposite angles | Equal |
| Diagonals | Bisect each other |
3
The Pythagorean Theorem
a² + b² = c² (c = hypotenuse)
⚠️ Common Mistake
The Pythagorean theorem works ONLY for right triangles, and c must be the longest side (hypotenuse).
4
Worked Example
A right triangle has legs 6 and 8. Find the hypotenuse.
c = √(6² + 8²) = √(36 + 64) = √100 = 10
This is the classic 6-8-10 (a 3-4-5 scaled) triangle.
📌 Quick Recap — Master These
Before your test, make sure you can confidently do each of the following:
- Explain and apply Similarity and Proportion.
- Explain and apply Parallelograms.
- Explain and apply The Pythagorean Theorem.
- Explain and apply Worked Example.
Re-read any section above where you hesitate, then try the worked example again without looking.