CA Foundation · Quantitative Aptitude · Sets, Relations and Functions, Limits and Continuity
In a group of 60 traders in a market, 35 deal in cotton, 28 deal in silk, and 10 deal in both cotton and silk. How many traders deal in neither cotton nor silk?
Seven traders deal in neither. The union of cotton and silk dealers is 35 + 28 − 10 = 53, because the 10 who deal in both are counted twice. Subtracting 53 from the total of 60 leaves 7 traders outside both sets.
- A7Correct
- B3
- C17
- D13
Explanation
n(C ∪ S) = 35 + 28 − 10 = 53. Traders dealing in neither = 60 − 53 = 7. Check: only cotton 25, only silk 18, both 10 gives 53. The value 17 arises from forgetting to subtract the overlap in the union (63 would exceed 60) or other slips; 13 is wrongly 60 − 35 − 28 + 10 + ... errors, and 3 results from using 63 − 60.
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