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Class 12MathematicsSetsEasyLevel 10
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In a survey of 50 people, 28 use a mobile, 20 use a computer, and 10 use both. How many people use neither device?

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Answer and explanation

Correct answer: 12

First find the number using at least one device. By inclusion–exclusion, n(M ∪ C) = 28 + 20 − 10 = 38, because the 10 people using both devices would otherwise be counted twice. The number using neither device is the total minus this union: 50 − 38 = 12. Therefore, option B is correct.

Related tags

SetsUnionComplementWord-ProblemMathematicsClass 12 Mcq

Frequently asked questions

What is the correct answer to this question?

12

Why is this the correct answer?

First find the number using at least one device. By inclusion–exclusion, n(M ∪ C) = 28 + 20 − 10 = 38, because the 10 people using both devices would otherwise be counted twice. The number using neither device is the total minus this union: 50 − 38 = 12. Therefore, option B is correct.

Which subject and chapter does this question cover?

This is a Class 12 Mathematics question. Chapter: Sets.

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  3. 3Which is the correct roster form of B = {x : x is a prime divisor of 84}?
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  5. 5Which option is not an example of a well-defined set?
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