Question

In a survey, it was found out that 100 people don’t use Laptop, Mobile or wrist watches. 80 persons use all the three gadgets. There are 150 who use Laptop and Mobile, 200 who use Mobile and Wristwatch and 200 who use Laptop and Wristwatch. The number of people who use only Laptop, only Mobile and only Wristwatch is equal. If this survey was conducted on 1000 persons ,How many people use only Wristwatch?​

Answer 1

Answer:

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Step-by-step explanation:

=> Let the number of people that use only Facebook = only Twitter = only Whatsapp = x

=> AUBUC = A + B + C - (A n B + B n C + C n A) + (A n B n C)

=> We can see that x + x + x + 80 + 200 + 200 + 150 + 100 = 1000

⇒ 3x = 1000 – 730

⇒ x = 270/3 = 90

=> x = 90

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Answer 2

Answer:

Let n(A) be the number of people who prefer tea , the number of people who prefer coffee be n(B) and n(A∩B) be the people who liked both.

Using the formula: n(A∪B) = n(A) + n(B) – n(A∩B)

n(A∪B) = 160 + 120 – 40 = 240