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Find the smallest positive integer (N) with the following property: of the three numbers (N), (N+1), and (N+2), one of them is divisible by (2^2), one of them is divisible by (3^2), one is divisible by (5^2), and one is divisible by (7^2).

a) 630
b) 882
c) 1260
d) 1764

User Bubuxu
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1 Answer

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Final answer:

The smallest positive integer N that satisfies the given divisibility conditions by the squares of the primes 2, 3, 5, and 7 is 1764. It is the only option where N, N+1, and N+2 are each divisible by a different one of these squares.

Step-by-step explanation:

The question requires finding the smallest positive integer N such that N, N+1, and N+2 are each divisible by the squares of different primes: 2, 3, 5, and 7. To solve this problem, we need to consider the divisibility conditions for each number:

  • A number is divisible by 2^2 (4) if its last two digits form a number divisible by 4.
  • A number is divisible by 3^2 (9) if the sum of its digits is divisible by 9.
  • A number is divisible by 5^2 (25) if its last two digits are 00, 25, 50, or 75.
  • A number is divisible by 7^2 (49) only if it satisfies the divisibility rule of 49, which is more complex and typically requires direct division to verify.

Through testing each option, we determine that:

  • 630 is divisible by 5^2 and 7^2, but 631 and 632 are not divisible by 2^2 or 3^2.
  • 882 is divisible by 2^2, 883 is not divisible by 3^2 or 5^2, and 884 is divisible by 2^2 again, failing the requirement.
  • 1260 is divisible by 2^2, 1261 is not divisible by 3^2, and 1262 is divisible by 2^2, so it also fails.
  • 1764 is divisible by 7^2, 1765 is divisible by 5^2, and 1766 is divisible by 2^2, meeting all the requirements.

Therefore, the smallest positive integer N with the given property is 1764.

User Jtooker
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