Question

If n(AuB) =25, n(A) =12, n(A-B) =8, then write the number of elements in B-A​

Answer 1

n (AUB) = n (A)+n (B)-n (AnB)

25=12+n (B)-4

25=8+n (B)

17=n (B)

n (B-A)=17-4=13

Answer 2

Answer:

13 is the value of (B - A).

Step-by-step explanation:

Explanation:

Given, n(A ∪ B) = 25 , n (A) = 12 , n(A - B ) = 8

As we know the formula ,

n( A∩B ) = n (A) - n(A-B)

and n(A∪B) = n(A) + n(B) -  n(A∩B )

Step 1:

First we find the value of n( A∩B ).

So, from the formula of n( A∩B ) = n (A) - n(A-B),

⇒n( A∩B ) = 12 - 8 = 4

Now from the formula of n(A∪B) = n(A) + n(B) -  n(A∩B ).

⇒n(A∪B) = n(A) + n(B) -  n(A∩B )

⇒25 = 12 + n(B) - 4

⇒25 - 12 + 4 = n(B)

⇒25 - 8 = n(B)

⇒n(B) = 13.

Where n(B) = (B-A) = 13 .

Final answer:

Hence, the value of (B- A) is 13.

#SPJ3