NDA 2 2025 Maths, question 103

Topic: Probability

Q103

The probability that a family owns a laptop is $0.68$ ; that it also owns a desktop is $0.56$ . If the probability that it owns both is $0.48$ , then what is the probability that a randomly selected family owns a laptop or a desktop?

(a) $0.80$
(b) $0.76$ Correct answer
(c) $0.36$
(d) $0.28$

Solution.

Answer: (b) $0.76$

Use inclusion–exclusion: P(L∪D)=P(L)+P(D)−P(L∩D)=0.68+0.56−0.48=0.76.
The overlap is subtracted once because it was counted twice.