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RRB NTPC Number System & Simplification Questions
Practise number system & simplification (quantitative aptitude) for the RRB Non-Technical Popular Categories Examination: 10 multiple-choice questions, each with the correct answer and a worked explanation. Click an option to check it, or “New questions” for another set.
Number System & Simplification practice
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Q1.Find the next number in the series: 64, 81, 100, 121, 144, ?
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Answer: D — 169
Squares of consecutive numbers: 8², 9², … → 13² = 169.
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Q2.Find the LCM of 32 and 12.
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Answer: B — 96
LCM(32, 12) = 96. Check: HCF × LCM = 4 × 96 = 384 = product of the numbers.
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Q3.Find the HCF of 16 and 72.
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Answer: A — 8
HCF(16, 72) = 8. Check: HCF × LCM = 8 × 144 = 1152 = product of the numbers.
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Q4.Simplify: 36 + 12 × 9 − 48
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Answer: B — 96
BODMAS: multiply first — 12 × 9 = 108; then 36 + 108 − 48 = 96.
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Q5.What is √7,921?
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Answer: D — 89
89 × 89 = 7921, so √7921 = 89.
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Q6.Find the next number in the series: 6, 11, 16, 21, 26, ?
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Answer: B — 31
Each term increases by 5.
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Q7.Simplify: 75 + 8 × 9 − 46
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Answer: C — 101
BODMAS: multiply first — 8 × 9 = 72; then 75 + 72 − 46 = 101.
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Q8.Simplify: 59 + 7 × 4 − 26
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Answer: A — 61
BODMAS: multiply first — 7 × 4 = 28; then 59 + 28 − 26 = 61.
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Q9.Find the LCM of 16 and 16.
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Answer: C — 16
LCM(16, 16) = 16. Check: HCF × LCM = 16 × 16 = 256 = product of the numbers.
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Q10.Find the next number in the series: 49, 64, 81, 100, 121, ?
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Answer: A — 144
Squares of consecutive numbers: 7², 8², … → 12² = 144.
How to approach number system & simplification questions
Learn squares to 30 and cubes to 15, apply BODMAS strictly, and use HCF × LCM = product of two numbers. For series, check the differences first, then the ratios.
About RRB NTPC
RRB Non-Technical Popular Categories Examination — conducted by Railway Recruitment Boards (RRB). Recruits clerks, station masters, goods guards and other non-technical posts for Indian Railways.
Original practice questions written for this site in the style and difficulty of each exam’s syllabus. They are not past papers and the site is not affiliated with any exam body. Exam patterns, marking schemes and syllabi change — always check the latest official notification.
RRB NTPC practice topics
| Topic | Section | Question source |
|---|---|---|
| Number System & Simplification | Quantitative aptitude | Calculated (new numbers every set) |
| Percentages | Quantitative aptitude | Calculated (new numbers every set) |
| Time, Work & Pipes | Quantitative aptitude | Calculated (new numbers every set) |
| Logical Reasoning | Reasoning | Calculated (new numbers every set) |
| Indian Polity, History & Geography | General awareness | Question bank |
| Physics | Science | Calculated + question bank |