Odd Man Out: Number Series Questions and Examples

Odd man out is a pattern-based aptitude topic where one number, word or value does not follow the rule followed by the others. This tutorial is made for students preparing for SSC, railway, banking, police, defence, state exams, teaching exams and placement aptitude tests. The focus is on simple explanation and more examples, because competitive exam maths improves only when a student solves many question patterns.

Recent ranking aptitude pages usually include formula revision, solved MCQs, shortcut tricks and practice tests. This page follows the same useful pattern, but keeps the language easy. The questions are competitive-exam style questions based on common patterns. They are not claimed as exact official previous-year questions.

Read the rule first, then solve the example, then try the practice questions. If you make a mistake, check whether it happened because of formula confusion, calculation error, unit error or hurry.

What is Odd Man Out?

Odd Man Out is an important maths topic because it builds calculation skill and question-reading skill. In written exams, a question may be asked directly or mixed with another chapter. So do not memorize only one fixed format. Learn the idea behind the question.

Important subtopics

Odd one in number series
Prime number pattern
Square pattern
Cube pattern
Even and odd pattern
Divisibility pattern
Alphabet-number pattern
Mixed reasoning

Basic rules to remember

Read the question carefully before starting calculation.
Find what is given and what is asked.
Check whether the answer should be a number, percentage, option, statement or unit.
Use a shortcut only when it is reliable for that question type.
In mixed questions, solve one small part at a time.
After getting the answer, check whether it is reasonable.

Solved examples for Odd Man Out

Example 1

Question: Find the odd one: 4, 9, 16, 25, 36, 49, 55.

Solution: All except 55 are perfect squares. 55 is not a square. Answer: 55.

Example 2

Question: Find the odd one: 2, 3, 5, 7, 11, 15, 17.

Solution: All except 15 are prime numbers. Answer: 15.

Example 3

Question: Find the odd one: 8, 27, 64, 100, 125, 216.

Solution: All except 100 are perfect cubes. Answer: 100.

More competitive exam examples

Example 4: Percentage

Question: Find 18% of 650.

Solution: 10% = 65, 8% = 52. Total = 117. Answer: 117.

Example 5: Average

Question: Average of 12, 18, 24, 30 and 36 is what?

Solution: Sum = 120. Average = 120/5 = 24.

Example 6: Ratio

Question: A sum of Rs 1080 is divided in 4:5. Find shares.

Solution: Total parts = 9. One part = 120. Shares are 480 and 600.

Example 7: Profit

Question: CP is Rs 700 and SP is Rs 805. Find profit percent.

Solution: Profit = 105. Profit percent = 105/700 × 100 = 15%.

Example 8: Simple Interest

Question: Find SI on Rs 2500 at 12% for 2 years.

Solution: SI = 2500 × 12 × 2 / 100 = Rs 600.

Example 9: Time and Work

Question: A can finish work in 16 days and B in 24 days. Find time together.

Solution: One day work = 1/16 + 1/24 = 5/48. Time = 48/5 = 9.6 days.

Example 10: Speed

Question: A train covers 300 km in 5 hours. Find speed.

Solution: Speed = 300/5 = 60 km/h.

Example 11: Area

Question: Find area of triangle with base 30 cm and height 18 cm.

Solution: Area = 1/2 × 30 × 18 = 270 square cm.

Example 12: Algebra

Question: Solve 6x – 7 = 29.

Solution: 6x = 36, so x = 6.

Example 13: Statistics

Question: Find range of 11, 19, 25, 31.

Solution: Range = 31 – 11 = 20.

Practice questions with answers

Find 25% of 760. Answer: 190.
A number is reduced by 15% and becomes 850. Find original number. Answer: 1000.
Find average of 7, 14, 21, 28, 35. Answer: 21.
Divide 1440 in the ratio 7:5. Answer: 840 and 600.
Find profit percent if CP is Rs 850 and SP is Rs 1020. Answer: 20%.
Find simple interest on Rs 4800 at 5% for 3 years. Answer: Rs 720.
A car travels 180 km in 2.5 hours. Find speed. Answer: 72 km/h.
Find area of a circle of radius 7 cm. Answer: 154 square cm.
Solve 5x + 10 = 60. Answer: 10.
Find next term: 11, 22, 44, 88, ?. Answer: 176.
Find HCF of 48 and 72. Answer: 24.
Find LCM of 9 and 15. Answer: 45.
Find median of 10, 3, 8, 15, 6. Answer: 8.
Find probability of getting an odd number on a dice. Answer: 1/2.
Find unit digit of 3⁴. Answer: 1.

Detailed practice solutions

Question 1

Find 25% of 760.

Answer: 190.

Explanation: First identify the topic. Then write the formula or pattern. Calculate step by step and check whether the answer fits the question. This method is useful in competitive exams because it reduces silly mistakes.

Question 2

A number is reduced by 15% and becomes 850. Find original number.

Answer: 1000.

Question 3

Find average of 7, 14, 21, 28, 35.

Answer: 21.

Question 4

Divide 1440 in the ratio 7:5.

Answer: 840 and 600.

Question 5

Find profit percent if CP is Rs 850 and SP is Rs 1020.

Answer: 20%.

Question 6

Find simple interest on Rs 4800 at 5% for 3 years.

Answer: Rs 720.

Question 7

A car travels 180 km in 2.5 hours. Find speed.

Answer: 72 km/h.

Question 8

Find area of a circle of radius 7 cm.

Answer: 154 square cm.

Question 9

Solve 5x + 10 = 60.

Answer: 10.

Question 10

Find next term: 11, 22, 44, 88, ?.

Answer: 176.

Question 11

Find HCF of 48 and 72.

Answer: 24.

Question 12

Find LCM of 9 and 15.

Answer: 45.

Shortcut tricks

For percentage questions, remember common fractions. 50% is 1/2, 25% is 1/4, 20% is 1/5, 12.5% is 1/8 and 10% is 1/10. This makes mental calculation faster.

For number pattern questions, check differences first. If differences do not work, check multiplication, squares, cubes, prime numbers and alternate terms. Do not force one pattern on every question.

For geometry and mensuration questions, draw a rough figure. A small figure helps you avoid using the wrong formula. Always write unit: cm, m, square cm, cubic cm, km/h or m/s.

Common mistakes

Using a formula without checking what the question asks.
Forgetting unit conversion.
Confusing percentage increase and percentage decrease.
Not arranging numbers before finding median.
Missing hidden words like only, at least, both, total and difference.
Spending too much time on one question.

Revision method

Revise this topic by solving examples in three levels. First solve direct formula questions. Next solve mixed questions. Finally solve timed questions. Keep wrong questions separately and revise them after two days. This is more useful than reading the same definition again.

For competitive exams, practice should be recent in style. Current aptitude pages focus on mixed practice, formula recall and answer explanation. So while preparing, solve questions from different chapters together after completing basic topic-wise practice.

FAQ on Odd Man Out

Is Odd Man Out asked in government exams?

Yes, it appears in maths, aptitude, numerical ability or reasoning-based sections depending on the exam.

How many examples should I solve?

Solve at least 30 to 50 questions from the topic, then solve mixed questions with a timer.

What is the best way to avoid mistakes?

Read the last line of the question carefully, keep units clear and revise your wrong questions.

Are these exact exam questions?

No. These are competitive exam style practice questions based on common patterns for learning and revision.

Conclusion

Odd Man Out becomes easier with regular practice and clear methods. Learn the rule, solve many examples and check your mistakes honestly.