Mathematics is where the KJSEA is won or lost for many Grade 9 learners. The good news is that the paper rewards method, not memorisation: if your child can show clear working, the marks follow. This guide walks through ten worked examples that cover the sub-strands examiners return to year after year, drawn straight from our KJSEA Grade 7-9 Complete Revision Course. You can also see a free sample first to check the standard.
The 2026 national assessment runs from 26 October to 20 November, so there is still time to revise the whole Grade 7 to 9 cycle properly. Work through each example below on paper, then check the steps.
Numbers
1. Order of operations (BODMAS)
Evaluate 4 + 3 × (10 − 6)2. Brackets first: (10 − 6) = 4. Then powers: 42 = 16. Then multiply: 3 × 16 = 48. Finally add: 4 + 48 = 52. The single most common error here is adding before multiplying, always follow the order.
2. LCM and GCD by prime factorisation
Find the GCD and LCM of 24 and 36. Write each as primes: 24 = 23 × 3 and 36 = 22 × 32. The GCD uses the lowest powers of the shared primes: 22 × 3 = 12. The LCM uses the highest powers of all primes: 23 × 32 = 72.
3. Percentage and discount
A shirt costing KSH 800 is reduced by 15%. Discount = (15/100) × 800 = KSH 120, so the new price is 800 − 120 = KSH 680. Always take the percentage of the original amount, not the rounded one.
4. Compound interest
Find the compound interest on KSH 20,000 at 10% per annum for 2 years. Amount = 20,000 × (1.1)2 = 20,000 × 1.21 = 24,200. Interest = 24,200 − 20,000 = KSH 4,200.
Algebra
5. Solving a linear equation
Solve 5x − 7 = 2x + 8. Collect terms: 5x − 2x = 8 + 7, so 3x = 15 and x = 5. Substitute back to check: 5(5) − 7 = 18 and 2(5) + 8 = 18. Correct.
6. Simultaneous equations
Solve x + y = 11 and x − y = 3. Add the two equations: 2x = 14, so x = 7. Then y = 11 − 7 = 4. Answer: x = 7, y = 4.
7. Forming and solving from words
A rectangle's length is 3 cm more than its width and its perimeter is 26 cm. Let the width be w. Then 2(w + w + 3) = 26, so 4w + 6 = 26 and w = 5. The length is 8 cm and the width is 5 cm. Defining the variable first is what earns the method marks.
Measurement and Geometry
8. Area and perimeter
A rectangle is 8 cm by 5 cm. Perimeter = 2 × (8 + 5) = 26 cm. Area = 8 × 5 = 40 cm2. Remember the units: length in cm, area in cm2.
9. Pythagoras
A ladder 13 m long has its foot 5 m from a wall. How high does it reach? h2 = 132 − 52 = 169 − 25 = 144, so h = √144 = 12 m.
Data and Ratio
10. Sharing in a ratio
Share KSH 7,200 among A, B and C in the ratio 2 : 3 : 4. Total parts = 2 + 3 + 4 = 9. One part = 7,200 ÷ 9 = 800. So A = 1,600, B = 2,400 and C = 3,200. Always check your three answers add back to the total.
How marks are actually earned in KJSEA Maths
- Show every step. Method marks are awarded even when the final answer slips.
- Mind your units. A missing cm2 or KSH can cost a mark.
- Define variables in word problems, and end with a clear concluding statement.
- Round only at the end, and to the accuracy the question asks for.
Revise the whole cycle, not just past papers
These ten examples are a start, but a strong result comes from covering every sub-strand across Grade 7, 8 and 9. Our KJSEA Complete Revision Course gives you full notes with worked examples, a topical question bank with marking schemes, and format-accurate mock papers, for all nine examinable subjects, from KSH 150 per subject or KSH 400 for the whole bundle. For a study plan to go with it, read how to revise for KJSEA 2026, and join our free Facebook community for updates and support.
Frequently asked questions
How many subjects does KJSEA examine?
Nine examinable learning areas, including Mathematics. Read our explainer on KJSEA grading and placement for how the scores feed Senior School selection.
When is KJSEA 2026?
The national assessment window is 26 October to 20 November 2026.
Where can I see the standard before buying?
Open the free KJSEA sample, it shows real notes, questions and marking schemes.
All 9 Grade 9 learning areas in one 144-page download: full-cycle notes, topical questions with marking schemes, and mock papers. KSH 400 instead of KSH 1,350 bought separately. See exactly what is inside or get the bundle here.
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