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Aptitude Topics

Divisibility Rules

Divisibility rules help solve aptitude questions faster by checking divisibility through simple digit-based tests instead of lengthy calculations.

Fundamental Principles

Divisibility

A number is divisible by another number if the remainder is zero after division.

Divisibility Rule

A shortcut method used to determine whether a number can be divided exactly by another number.

Essential Formulation Tips

  • Always start with simple rules such as 2, 5, and 10.
  • For 3 and 9, use the sum of digits.
  • For 4 and 8, focus on the last few digits only.
  • Practice common divisibility tests to improve speed.

Shortcut Execution Techniques

  • Divisible by 2 → Last digit is even.
  • Divisible by 3 → Sum of digits is divisible by 3.
  • Divisible by 4 → Last two digits form a number divisible by 4.
  • Divisible by 5 → Last digit is 0 or 5.
  • Divisible by 6 → Number is divisible by both 2 and 3.
  • Divisible by 8 → Last three digits form a number divisible by 8.
  • Divisible by 9 → Sum of digits is divisible by 9.
  • Divisible by 10 → Last digit is 0.

Contextual Inquiries (FAQs)

Q: How do I check divisibility by 3?

A: Add all digits. If the sum is divisible by 3, the number is divisible by 3.

Q: How do I check divisibility by 4?

A: Check whether the last two digits form a number divisible by 4.

Q: Why are divisibility rules important in aptitude exams?

A: They help solve HCF, LCM, factors, and number system questions quickly.