Discussion

In a group of 52 people, 16 drink tea but not coffee and 33 drink tea. How many drink coffee but not tea?

Answer: B

Let T be for tea and C for coffee. n(T only) = 16, n(T) = 33. Total = 52.

We can find the number who drink both: n(T ∩ C) = n(T) - n(T only) = 33 - 16 = 17.

The union of the sets (people who drink tea or coffee or both) is n(T ∪ C) = n(T only) + n(C only) + n(both) = 16 + n(C only) + 17.

Since everyone is assumed to drink something, total = n(T ∪ C). So, 52 = 16 + n(C only) + 17 = 33 + n(C only).

n(C only) = 52 - 33 = 19.

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