Aptitude Problems on Permutation and Combination – Tips and Tricks to Solve in IBPS PO and Clerk Exams with examples.
Hello Students, I am Rahul Sir, and today we will discuss one of the most important topics in the Quantitative Aptitude section of IBPS PO and Clerk examinations – Permutation and Combination. Many banking aspirants find this topic difficult because it involves counting arrangements and selections without actually listing all possibilities. However, once you understand the basic concepts and formulas, these questions become among the easiest scoring areas in competitive exams. Permutation and Combination questions test your logical thinking, counting ability, and understanding of arrangements. They are frequently asked in IBPS PO, IBPS Clerk, SBI PO, SBI Clerk, RRB PO, and other banking examinations. Usually, 1-3 questions appear directly or indirectly from this topic. In this article, I will explain important concepts, formulas, shortcuts, and exam-oriented tricks with examples. By mastering these techniques, you can solve questions quickly and accurately during the exam. 1. Understanding Permutation and Combination Basics Before learning shortcuts, it is important to understand the difference between permutation and combination. Permutation Permutation refers to arrangements where order matters. Formula: nPr = n! / (n-r)! Combination Combination refers to selections where order does not matter. Formula: nCr = n! / [r!(n-r)!] Example How many ways can 3 students be selected from 5 students? Combination: 5C3 = 5! / (3! × 2!) = 10 How many ways can President, Vice President, and Secretary be selected from 5 students? Permutation: 5P3 = 5! / 2! = 60 Exam Tip Whenever positions are different, use permutation. Whenever only selection is required, use combination. Quick Memory Trick Most exam mistakes happen because students confuse these two concepts. 2. Mastering Factorials Quickly Factorials are the foundation of permutation and combination. Formula n! = n × (n-1) × (n-2) … Examples 5! = 120 6! = 720 7! = 5040 Important Values Number Factorial 1 1 2 2 3 6 4 24 5 120 6 720 7 5040 Shortcut Instead of calculating complete factorials, cancel terms. Example: 8! / 6! = (8×7×6!)/6! = 56 Example Question Find 10P2. 10P2 = 10!/8! = 10 × 9 = 90 Exam Strategy Memorize factorial values up to 10!. This saves significant time during calculations. 3. Circular Arrangement Questions Questions involving people sitting around a table are common. Formula For n persons sitting in a circle: Arrangement = (n-1)! Example How many ways can 6 persons sit around a round table? =(6−1)! =5! =120 Why? In circular arrangements, rotations are considered identical. Example A B C D and B C D A are same arrangements in a circle. Quick Tip Situation Formula Straight Line n! Circle (n-1)! Example 8 persons around a table: (8−1)! =7! =5040 This shortcut frequently appears in banking and insurance exams. 4. Arrangements with Repeated Letters Many questions involve words containing repeated letters. Formula n! / (p! × q! × r!) Where p, q, r are repeated letters. Example Find arrangements of “LEVEL” Letters = 5 Repeated: L = 2 E = 2 Answer: 5!/(2!×2!) =120/4 =30 Example Find arrangements of “BANANA” Total letters = 6 A = 3 N = 2 Answer: 6!/(3!×2!) =720/12 =60 Shortcut Always identify repeated letters before applying factorial. Ignoring repetitions leads to incorrect answers. 5. Selection of Committees Committee questions are pure combination-based problems. Example A committee of 4 members is to be formed from 10 people. 10C4 =210 Example Choose 2 boys from 5 and 3 girls from 7. Required: 5C2 × 7C3 =10 × 35 =350 Shortcut When separate groups exist: Use multiplication. Formula Total Ways = Ways from Group A × Ways from Group B Committee questions are among the easiest permutation-combination questions in IBPS exams. 6. Arrangements with Restrictions Many questions contain conditions. Example How many ways can 5 persons sit if A and B sit together? Treat A and B as one unit. Units become: AB, C, D, E Total units = 4 Arrangement: 4! Internal arrangement of AB: 2! Answer: 4! × 2! =24 × 2 =48 Shortcut When people stay together: This method solves most restriction-based questions quickly. 7. Arrangements Where Persons Cannot Sit Together Opposite of the previous concept. Example Arrange A, B, C, D, E where A and B cannot sit together. Method Total arrangements =5! =120 Arrangements where A and B sit together =4! × 2! =48 Required =120−48 =72 Shortcut Formula Required = Total Arrangements − Restricted Arrangements This method saves time compared to direct counting. 8. Formation of Numbers Using Digits Questions often involve forming numbers from digits. Example How many 3-digit numbers can be formed using digits 1,2,3,4,5? Use permutation. 5P3 =5×4×3 =60 Example How many 4-digit numbers can be formed using 0,1,2,3,4? First digit cannot be zero. Choose first digit: 4 ways Remaining: 4P3 =24 Total =4×24 =96 Shortcut Whenever zero exists: Handle first digit separately. This avoids common mistakes. 9. Shortcut Techniques for IBPS Exams Important Results nC0 = 1 nCn = 1 nC1 = n nCn−1 = n Symmetry Property nCr = nCn−r Example: 10C8 = 10C2 =45 Benefit Always choose the smaller value of r. Example: 15C13 Instead solve 15C2 =105 Much faster. Exam Trick Reduce calculations by applying symmetry before solving. This saves valuable exam time. 10. Previous Year IBPS Style Questions Question 1 Select 3 members from 8 persons. 8C3 =56 Question 2 Arrange 5 books on a shelf. 5! =120 Question 3 How many ways can 7 students stand in a row? 7! =5040 Question 4 How many ways can 2 boys and 3 girls be selected from 5 boys and 6 girls? 5C2 × 6C3 =10 × 20 =200 Question 5 Arrange the letters of “BOOK”. 4! / 2! =12 Exam Advice Practice at least 50 mixed-level questions before the exam. The more patterns you solve, the faster you identify the correct approach. How Teachers from OdTutor Can Help At OdTutor, experienced aptitude faculty help students master Permutation and Combination through concept-based learning, shortcut techniques, and extensive practice sessions. Our teachers explain difficult concepts using simple real-life examples and exam-oriented methods. Students receive topic-wise worksheets, doubt-solving









