Conjunction

A conjunction is a statement formed by adding two statements with the connector AND. The symbol for conjunction is ‘∧’ which can be read as ‘and’. When two statements p and q are joined in a statement, the conjunction will be expressed symbolically as p∧q. If both the combining statements are true then this statement will be true otherwise, it is false.

Conjunction

Rules for a conjunction to be true

  • The conjunction statement will only be true if both the combining statements are true otherwise, the disjunction is false.
  • It is similar to an AND gate which is utilized under the topic Gate logic.
  • The definition is stated as let p and q be the two statements. The compound statement p ∧ q is called as the conjunction of p and q.
  • The symbol “∧” that denotes the conjunction is called as “and” which is the logical connective.

Conjunction Truth Table

P Q P ∧ Q
T T     T
T F     F
F T     F
F F     F

In this table, we can say that the conjunction is true only when both P and Q are true. If they are not then the conjunction statement will be false.

Solved Problems:

Example 1: Let r: 5 be a rational number and s: 15 be a prime number. Is it a conjunction?

Solution:

Given that r: 5 is a rational number. This proposition is true.

s: 15 is a prime number. This proposition is false as 15 is a composite number.

Therefore, as per the truth table, r and s is a false statement.

So, r ∧ s = F

Example 2: Let a: x is greater than 9 and b: x be a prime number. Is it a conjunction?

Solution:

Since x is a variable whose value we don’t know. Let us define a range for a and b.

To find the range let us take certain values for x;

When x= 6: a is false so is b hence a ∧ b is false.

When x= 3: a is false but b is true. But still, a ∧ b is false.

When x= 10: a is true but b is false. But still, a ∧ b is false.

When x= 11: a is true and b is true. Hence, a ∧ b is true.

Hence the conjunction a and b is only true when x is a prime number greater than 9.


Practise This Question

Maurice applied for a job and got selected. She has been offered a job with a starting monthly salary Rs.10000. If annual increment in her salary is Rs.400, form a series for her monthly salary for first six years. Is this series an AP?