A market research group conducted a survey of 2,000 consumers and reported that 1720 consumers liked product P1 and 1,4500 consumers liked product P2. What is the least number that must have liked both the products.
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Solution
Total consumer = 2000
P1 liked by = 1720
P2 liked by = 1450
∴N(P1∪P2)=N(P1)+N(P2)−N(P1∩P2)
⇒2000=1720+1450−N(P1∩P2)
⇒N(P1∩P2)=3170−2000
⇒1170
∴ least no : of people = 1170 liked both products.