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.