If A is the set of prime numbers and B is the set of 2 digit positive integers whose unit digit is 5, how many numbers are in common for both sets?
A) NONE B) ONE C) TWO D) SEVEN E) NINE ANSWER: Choice A Set A {1,3,5,7,11,13,17,19,......} --> Set of Prime Numbers (Numbers that have only two factors: "1" and "itself") Set B {15,25,35,45,55,......} -->Set of two digit positive integers whose unit digit (ones place) is "5" Each two digit positive integer with a unit digit of 5 has more than 2 factors, each of these numbers is Set B has 1, 5, and "itself" as a factor. Therefore these two sets are disjoint (sharing no common element). Therefore Choice A is the correct answer.
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Math Problem of the Day ANSWERS PART II
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