Distribution Problem

Distribution problems involve distributing objects into boxes or recipients. When objects are distinct and boxes are distinct, each object has independent choices, so the number of ways is (number of boxes)^(number of objects). Different variations include empty boxes allowed or not, identical objects, or identical boxes.

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200+Practice Questions
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2-3 hoursHours to Master

Introduction to Distribution Problem

Distribution problems involve distributing objects into boxes or recipients. When objects are distinct and boxes are distinct, each object has independent choices, so the number of ways is (number of boxes)^(number of objects). Different variations include empty boxes allowed or not, identical objects, or identical boxes.

Prerequisites

Fundamental Counting Principle Multiplication vs addition Understanding of 'distinct' vs 'identical' Stars and bars basics
Why This Matters: Distribution problems appear in 1-2 questions in SSC CGL and Banking exams. They test application of multiplication principle to real-world distribution scenarios.

How to Solve Distribution Problem Problems

1

Step 1: Identify if objects are distinct or identical

2

Step 2: Identify if boxes/recipients are distinct or identical

3

Step 3: Determine if empty boxes are allowed

4

Step 4: For distinct objects, distinct boxes, empty allowed: use kⁿ

5

Step 5: For distinct objects, distinct boxes, no empty: use inclusion-exclusion

6

Step 6: For identical objects, distinct boxes: use stars and bars

7

Step 7: For identical objects, identical boxes: use partition theory (advanced)

Pro Strategy: First, classify the problem: distinct/identical objects? distinct/identical boxes? empty allowed? Then apply the appropriate formula. For distinct objects into distinct boxes with no empty, use Stirling numbers of the second kind multiplied by factorial.

Example Problem

Example: In how many ways can 5 different gifts be distributed among 3 children? (Empty allowed) Solution: Step 1: Gifts are distinct, children are distinct Step 2: Empty boxes allowed Step 3: Each gift can go to any of 3 children Step 4: Total ways = 3⁵ = 243 Answer: 243 ways

Pro Tips & Tricks

  • Distinct objects, distinct boxes, empty allowed: kⁿ
  • Distinct objects, distinct boxes, no empty: k! × S(n,k) (Stirling number)
  • Identical objects, distinct boxes, empty allowed: C(n+k-1, k-1) (stars and bars)
  • Identical objects, distinct boxes, no empty: C(n-1, k-1)
  • When distributing distinct objects, each object is independent
  • When distributing identical objects, use combinations not permutations

Shortcut Methods to Solve Faster

kⁿ for distinct objects, distinct boxes, empty allowed
C(n+k-1, k-1) for identical objects, distinct boxes, empty allowed
C(n-1, k-1) for identical objects, distinct boxes, no empty
If objects are 'given' rather than 'distributed', they are typically distinct

Common Mistakes to Avoid

Using stars-and-bars for distinct objects (should use kⁿ)
Forgetting to consider whether empty boxes are allowed
Confusing distribution (objects to boxes) with selection (choosing from groups)
Not distinguishing between distinct and identical objects

Exam Importance

Distribution Problem is an important topic for various competitive exams. Here's how frequently it appears:

SSC CGL
1-2 questions
BANKING PO
1-2 questions
RAILWAYS RRB
1-2 questions
CAT
1-2 questions
INSURANCE
1-2 questions

Ready to Master Distribution Problem?

Start with Worksheet 1 and work your way up to expert level! Each worksheet includes:

20 practice questions
Detailed solutions
Step-by-step explanations
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