Last Updated:
This Number System question develops accurate interpretation and stepwise calculation for “Which one of the following is not a prime number?”.
Apply prime factorisation and count only factors that satisfy the condition in the stem. The question-specific working recorded with the item is: 33 is divisible by 3 and 11 so it is not a prime number.. Write one justified transformation per line, cancel common factors only when multiplication permits it, and preserve the left-to-right rule for operations of equal priority.
FAQ
Common questions and clear answers for this topic.
Apply prime factorisation and count only factors that satisfy the condition in the stem.
33, option C.
Changing operation order, losing a sign, or simplifying a factor where cancellation is invalid.
Substitute it back, estimate its magnitude, or recompute using an equivalent form.
Number System covers Natural Numbers (1,2,3), Whole Numbers (0,1,2,3), Integers, Rational Numbers (p/q form), Irrational Numbers (like pi and root 2), and Real Numbers. For competitive exams like SSC CGL and IBPS, focus on: divisibility rules, LCM and HCF, factors, prime numbers, and unit digit calculations.
Divisibility rules: Divisible by 2 - last digit even. By 3 - sum of digits divisible by 3. By 4 - last two digits divisible by 4. By 5 - last digit 0 or 5. By 6 - divisible by both 2 and 3. By 8 - last three digits divisible by 8. By 9 - sum of digits divisible by 9. By 11 - difference of alternating digit sums divisible by 11. Mastering these rules helps solve Number System questions faster in competitive exams.
