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This Number System question develops accurate interpretation and stepwise calculation for “Which number is divisible by 18?”. The explanation preserves the original mathematical conditions, verifies 144, and identifies common errors involving signs, brackets, operation order, factors, remainders or fraction handling. The verified result is 144.
The verified answer is 144, option C. The question-specific working recorded with the item is: 144 divisible by 2 and 9.. The distractors 146, 147, 145 may arise from changing the order of operations, mishandling a negative sign, using an incorrect reciprocal, ignoring a divisibility condition, or rounding an exact value.
FAQ
Common questions and clear answers for this topic.
Use divisibility rules or modular arithmetic, reducing large values before calculation.
144, 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.
