Question

Out of 300 people, 75 people use only Viber and 45 people use only Skype. 90 people use both Skype and Viber.
people use neither Viber nor Skype.

• A. 225
• B. 255
• C. 90
• D. 180

Answer 1

The correct option is C 90

Let U denote the set of surveyed mobile users. V denotes set of people using Viber and S denote set of people using Skype. Then, n(U) = 300, n(V ∩ S) = 90.

Number of people who use only Viber = 75

So, total number of people who use Viber n(V) = 75+90 = 165

Similarly, It is given that the number of people who use only Skype = 45

So, total number of people who use Skype n(S) = 45 + 90 = 135

now, no. of persons who use neither Viber nor Skype is given as,

n(V^I ∩ S^I) = n(V ∪ S)^I

= n(U) - n(V ∪ S)

= n(U) - [n(V) + n(S) – n(V∩S)]

= 300 - (165 + 135 - 90)

= 300 - 210

= 90