Word Problems Based on Relations

Simple word problems involving relations with clear step-by-step interpretation into ordered pairs.

1. How to Approach Word Problems on Relations

Word problems often describe connections using everyday language. The goal is to translate these descriptions into ordered pairs. Once written as a relation, it becomes easier to analyse, interpret, or present the information using tables, lists, or diagrams.

2. Identifying the Sets

First, decide which sets are involved. A word problem usually mentions two groups of objects: people, numbers, cities, items, or options. These become the sets A and B.

2.1. Example

If the problem talks about three students and two sports they like, then:

A = \{\text{students}\}, \; B = \{\text{sports}\}

3. Extracting Ordered Pairs

Look for statements that show how one item connects to another. Each connection becomes an ordered pair (a,b). This is the heart of converting a word problem into a relation.

3.1. Example

“A likes football” becomes (A, football).
“B likes cricket” becomes (B, cricket).

4. Example Problem 1 — Preferences

Problem: Three children {A, B, C} choose from two fruits {apple, banana}. A and C choose apple, and B chooses banana.

4.1. Relation

R = \{(A, \text{apple}), (C, \text{apple}), (B, \text{banana})\}

5. Example Problem 2 — Distance

Problem: Cities {P, Q, R} and distances: P is connected to Q, Q to R, and P to R.

5.1. Relation

D = \{(P,Q),(Q,R),(P,R)\}

6. Example Problem 3 — Divisibility

Problem: In the set {1,2,3,4,6}, write the relation “a divides b”.

6.1. Relation

D = \{(1,1),(1,2),(1,3),(1,4),(1,6),(2,2),(2,4),(2,6),(3,3),(3,6),(4,4),(6,6)\}

7. Example Problem 4 — Friendship

Problem: In a group {A, B, C}, A is friends with B, and B is friends with C. The relation is one-way (not symmetric) because friendship here means A follows B on a website.

7.1. Relation

F = \{(A,B),(B,C)\}

8. Example Problem 5 — Ordering

Problem: In a list {x, y, z}, x comes before y, and y comes before z.

8.1. Relation

O = \{(x,y),(y,z),(x,z)\}

9. How These Problems Help

Word problems strengthen the ability to convert real situations into precise mathematical descriptions. Once written as ordered pairs, relations become easier to represent using tables, digraphs, and matrices, and to analyse for properties like symmetry, reflexivity, or transitivity.