Question

in a survey of people it is found that 70% liked curd , 60% liked milk , 20% didnt like any and 550 liked both. Find total no of people n(U)

Answer 1

N = 60

If you know Venn diagrams, then do that using circular areas for sets.  Let U denote the union symbol.  ∧ denotes intersection.  see diagram.

Coffee C = 25          Tea T = 26              Milk M = 24

C  ∧  M = 9            C  ∧  T = 11            T ∧ M = 8          C  ∧  T  ∧  M  = 3

1)    (C ∧ T) -  M  =   (C∧ T) -  (C ∧ T∧ M)  = 11 - 3 = 8

2)  add the number of persons in each colored region ie., each inside some circle.

   that gives the number of persons who like  some drink.  That comes to 50.

   the number of people who dont  like any drink = 60  -  50 = 10

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