CA Foundation · Quantitative Aptitude · Sets, Relations and Functions, Limits and Continuity
If A = {x : x is a natural number less than 8} and B = {x : x is an even natural number less than or equal to 10}, how many elements does A − B (elements in A but not in B) have?
A − B has 4 elements. Set A contains 1 to 7 and B contains the even numbers 2 to 10. The common elements are 2, 4 and 6, so removing them from A leaves {1, 3, 5, 7}.
- A3
- B4Correct
- C5
- D7
Explanation
A = {1,2,3,4,5,6,7}. B = {2,4,6,8,10}. A ∩ B = {2,4,6}. A − B = {1,3,5,7}, which has 4 elements. Check: 7 − 3 = 4. Option 3 is the size of the intersection, not the difference.
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