If the number of toursits who have visited at least one of the two cities Hong Kong and Singapore is 330, how many toursits visited only Hong Kong and Singapore?
Explanation:
Consider the solution to first question of this set.
The number of toursits who visited only Hong Kong and Singapore is denoted by z in the Venn diagram drawn above.
The set of toursits who visited at least one city from Hong Kong and Singapore implies the union of the two sets H and S.
This set is given as: S ∪ H = S + H − (S ∩ H)
∴ 330 = 190 + 190 − (z + 30)
∴ z = 380 − 30 – 330 = 20
Hence, 20 people visited only Hong Kong and Singapore
Hence, option (c).
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