Answer:
160
Step-by-step explanation:
From the formula,
n (AUB) = n(A) + n(B) - n(A n B).
(AUB) has the least value when (A n B) has maximum possible value.
Therefore,
n (AUB) = n(A) + n(B) - maximum value of n(A n B).
We find maximum value of n(A n B) first.
Since (A n B) is a subset of B, so n(A n B) cannot be greater than n(B) = 80.
Therefore, maximum value of n(A n B) = 80.
Hence,
n (AUB) = n(A) + n(B) - maximum value of n(A n B)
n (AUB) = 160 + 80 - 80
n (AUB) = 160 + 0
n (AUB) = 160
The least value of AUB is 160.
