CMA Foundation · Fundamentals of Business Mathematics and Statistics · Set Theory, including Venn Diagram
In a group of 60 customers of an Indian retail firm, 35 bought tea, 28 bought coffee, and 8 bought neither. How many bought both tea and coffee?
Customers buying at least one drink number 60 - 8 = 52. Using the union formula, 52 = 35 + 28 - both, so both = 63 - 52 = 11. Therefore 11 customers bought both tea and coffee.
- A11Correct
- B19
- C3
- D8
Explanation
Customers buying at least one = 60 - 8 = 52. n(T∪C) = n(T) + n(C) - n(T∩C), so 52 = 35 + 28 - x, giving x = 63 - 52 = 11. The option 3 results from wrongly using 60 as the union (63 - 60).
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