Module ·
Chapter 1: Number System & Simplification
Arithmetic
6 topics
What this chapter covers
The 6 topics below make up Number System & Simplification in the SSC CGL exam. Click any topic to open its notes, examples and practice test.
1Classification of Numbers
2Divisibility Rules
3HCF & LCM
4Factors & Unit Digit
5BODMAS & Simplification
6Surds & Indices
Study material & tests
📚 Study this chapter
Notes, worked examples and hint-guided practice for every topic.
Start learning →
🎯 Topic tests
8 auto-graded questions per topic, pulled from the question bank.
Practice by topic →
📝 Chapter test
25 fresh mixed-difficulty questions, timed, with full solutions.
Take chapter test →
Formula Reference Sheet
This chapter
HCF, LCM & products
| HCF x LCM | HCF(a,b) x LCM(a,b) = a x b |
|---|---|
| Numbers as multiples | a = HCF x m, b = HCF x n with m, n coprime |
| LCM of fractions | LCM = LCM(numerators) / HCF(denominators) |
| HCF of fractions | HCF = HCF(numerators) / LCM(denominators) |
Counting & series
| Sum 1..n | n(n+1)/2 |
|---|---|
| Sum of squares | n(n+1)(2n+1)/6 |
| Number of factors of N = p^a x q^b | (a+1)(b+1) |
| Sum of first n odd numbers | n^2 |
Indices & surds
| Product rule | a^m x a^n = a^(m+n) |
|---|---|
| Power of a power | (a^m)^n = a^(mn) |
| Rationalising | multiply by the conjugate to clear a surd denominator |
SSC reference
🖩 Graphing Calculator