CDS Mathematics · Teaching notes
Logarithms — CDS Elementary Mathematics
Logarithms has 33 past-year questions in CDS Elementary Mathematics, in 18 of the twenty-one sittings from 2016 (II) to 2026 (II). The laws of logarithms account for 13 of them, and five of the eight HARD items are equations: most answers come from breaking numbers into 2, 3, 5 and powers of 10. The pages go from the laws to counting digits and end with logarithmic and exponential equations.
Every subtopic, worked example, formula and trap in one printable document — answers shown, ready to share.
Subtopic notes
Laws of Logarithms
13 PYQsA logarithm is an exponent: log turns products into sums, powers into multiples, and any number into a combination of log 2, log 3 and log 5.
Counting Digits with Logarithms
10 PYQsA number whose common logarithm has integer part k has k + 1 digits before the decimal point.
Logarithmic and Exponential Equations
10 PYQsTurn a log equation into a power (log N = k means N = 10ᵏ), or take logs of an exponential equation, and solve what remains.
Formula & revision sheet
3 formulas · 4 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
3 formulas · 4 gotchas across all subtopics — the exam-eve cheat-sheet
Formulas (1)
Watch out for (1)
- The bar applies to the characteristic only→ Product, power and change of base
Formulas (1)
Watch out for (2)
- Add one→ Digits and leading zeros
- Zeros after the point: use the next power down→ Digits and leading zeros
Formulas (1)
Watch out for (1)
- Check the argument→ Unwrapping logs and taking logs
PYQ weightage by concept
3 concepts · 33 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
3 concepts · 33 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| Unwrapping logs and taking logs | 10 | 30% |
Test yourself on Logarithms
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.