CDS Mathematics · Teaching notes
Linear Equations — CDS Elementary Mathematics
Linear Equations has 40 past-year questions in CDS Elementary Mathematics, in 14 of the twenty-one sittings from 2016 (II) to 2026 (II). Word problems and age problems account for 25 of them; the rest ask to solve or classify a pair of equations, or to count whole-number solutions, where HARD items are densest (three of five).The pages go from solving two equations to word problems and ages, and end with whole-number solutions.
Every subtopic, worked example, formula and trap in one printable document — answers shown, ready to share.
Subtopic notes
Solving Two Equations
10 PYQsTwo linear equations in two unknowns meet in one point, in no point, or in every point, and the ratios of their coefficients tell you which.
Word Problems
13 PYQsName each unknown, turn each sentence into one equation, and solve; the arithmetic is simple once the equations are right.
Age Problems
12 PYQsWrite every age as a present age plus or minus the years that have passed; each 'was' or 'will be' sentence is then one linear equation.
Whole-Number Solutions
5 PYQsAn equation like 7a + 10b = 200 has only a few whole-number solutions; find one, then step to the others by the coefficients.
Formula & revision sheet
5 formulas · 5 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
5 formulas · 5 gotchas across all subtopics — the exam-eve cheat-sheet
Formulas (2)
Watch out for (2)
- Dividing by xy drops x = y = 0→ Elimination and substitution
- Both signs of k→ One solution, none, or infinitely many
Formulas (1)
Watch out for (1)
- The remainder must be smaller than the divisor→ From sentences to equations
PYQ weightage by concept
5 concepts · 40 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
5 concepts · 40 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Elimination and substitution | 6 | 15% |
| One solution, none, or infinitely many | 4 | 10% |
Test yourself on Linear Equations
15 past CDS questions from this chapter, timed at 18 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.