Divisibility Rules & Unit Digits

A high-yield practice drill on standard Divisibility Rules and Unit Digit calculation for Kerala PSC examinations (LDC, LGS, CPO, Fireman, Secretariat Assistant). Master shortcut divisibility tests ($$2, 3, 4, 5, 6, 8, 9, 10, 11$$), solving for missing digits to satisfy divisibility conditions, and unit digits in products and powers.

Study Scope

• Divisibility Tests: Sum of digits ($$3$$ and $$9$$), last two digits ($$4$$), last three digits ($$8$$), alternating sum difference ($$11$$)
• Co-prime Composite Divisibility: Testing for $$6$$ ($$2 \times 3$$), $$12$$ ($$3 \times 4$$), $$15$$ ($$3 \times 5$$)
• Missing Digit Puzzles: Finding the smallest digit to make numbers divisible by $$3, 9$$, or $$11$$
• Unit Digit Operations: Unit digits of arithmetic sums and large products
• Power Cyclicity: Cyclicity of base unit digits ($$2, 5, 6, 7$$) in power calculations

Tested Competencies

• Instantly determine whether a multi-digit number is divisible without long division
• Identify missing digits in algebraic arithmetic expressions
• Rapidly compute unit digits of large powers and products