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RRB JE Number System & Simplification Questions
Practise number system & simplification (quantitative aptitude) for the RRB Junior Engineer 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: 6, 8, 12, 18, 26, ?
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Answer: A — 36
Differences are 2, 4, 6, 8 → next difference 10.
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Q2.Find the HCF of 60 and 90.
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Answer: D — 30
HCF(60, 90) = 30. Check: HCF × LCM = 30 × 180 = 5400 = product of the numbers.
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Q3.What is √7,744?
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Answer: A — 88
88 × 88 = 7744, so √7744 = 88.
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Q4.What is √1,681?
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Answer: D — 41
41 × 41 = 1681, so √1681 = 41.
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Q5.What is √4,624?
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Answer: B — 68
68 × 68 = 4624, so √4624 = 68.
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Q6.Find the LCM of 56 and 63.
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Answer: D — 504
LCM(56, 63) = 504. Check: HCF × LCM = 7 × 504 = 3528 = product of the numbers.
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Q7.Simplify: 63 + 3 × 3 − 35
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Answer: B — 37
BODMAS: multiply first — 3 × 3 = 9; then 63 + 9 − 35 = 37.
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Q8.Find the LCM of 10 and 40.
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Answer: D — 40
LCM(10, 40) = 40. Check: HCF × LCM = 10 × 40 = 400 = product of the numbers.
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Q9.Find the next number in the series: 9, 16, 25, 36, 49, ?
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Answer: A — 64
Squares of consecutive numbers: 3², 4², … → 8² = 64.
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Q10.Find the HCF of 12 and 18.
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Answer: C — 6
HCF(12, 18) = 6. Check: HCF × LCM = 6 × 36 = 216 = product of the numbers.
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 JE
RRB Junior Engineer Examination — conducted by Railway Recruitment Boards (RRB). Recruits Junior Engineers, Depot Material Superintendents and Chemical & Metallurgical Assistants.
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 JE practice topics
| Topic | Section | Question source |
|---|---|---|
| Physics | Science | Calculated + question bank |
| Chemistry | Science | Calculated + question bank |
| Number System & Simplification | Quantitative aptitude | Calculated (new numbers every set) |
| Logical Reasoning | Reasoning | Calculated (new numbers every set) |
| Computer Awareness | Computer knowledge | Question bank |