Question

in a town 10000families it was found that 40%families buy newspaper A, 20%buy newspaper B , and 10% families buy C NEWSPAPER 5%buyAand B,3% BUY BandC ,4% buy Aand C if 2% buy all thev three families newspaper then no. of families which buy newspaper A only

Answer 1

Sets related problem.   For more clarity draw Venn diagrams.

N total = N (U ) = 10,000.
N(A) = 40% = 4,000
N(B) = 20% = 2,000
N(C) = 10% = 1,000

N(A ∧ B) = 5% = 500
N(B ∧ C) = 3% = 300
N(C ∧A) = 4% = 400

N(A ∧ B∧ C) = 2% = 200

We want N(A - A∧B - A∧C)
    = N(A) - N(A∧C) - N(A∧B) + N(A∧B∧C)
    = 4,000 - 400 - 500 + 200 
    = 3,300 
answer.

Answer 2

Sets related problem.   For more clarity draw Venn diagrams.

N total = N (U ) = 10,000.

N(A) = 40% = 4,000

N(B) = 20% = 2,000

N(C) = 10% = 1,000

N(A ∧ B) = 5% = 500

N(B ∧ C) = 3% = 300

N(C ∧A) = 4% = 400

N(A ∧ B∧ C) = 2% = 200

We want N(A - A∧B - A∧C)

    = N(A) - N(A∧C) - N(A∧B) + N(A∧B∧C)

    = 4,000 - 400 - 500 + 200 

    = 3,300 

answer.