Question

Difficulty: MediumPrime Numbers and Prime Factorization

Let N=24×32×5N = 2^4 \times 3^2 \times 5. How many distinct prime factors does the integer N+9N + 9 have?

  1. 1Answer
  2. B
    2
  3. C
    3
  4. D
    4
  5. E
    6

Answer

The integer N+9N + 9 has 1 distinct prime factor.
Evaluating N=24×32×5N = 2^4 \times 3^2 \times 5 gives 720720. Adding 9 yields 729729, which prime factorizes as 363^6. Because 3 is the only unique prime base in this expression, N+9N + 9 has exactly 1 distinct prime factor.

Step-by-Step Solution

1
Calculate the numerical value of NN from its prime factorization.
N=24×32×5=16×9×5=720N = 2^4 \times 3^2 \times 5 = 16 \times 9 \times 5 = 720
Evaluating NN is necessary to compute N+9N + 9.
2
Add 9 to NN to find the value of N+9N + 9.
N+9=720+9=729N + 9 = 720 + 9 = 729
The question asks for the distinct prime factors of the sum N+9N + 9.
3
Find the prime factorization of 729.
729=36729 = 3^6
Prime factorization reveals the prime bases of the integer.
4
Count the number of distinct prime factors of 729.
The only distinct prime factor is 3, so the count is 1.
Distinct prime factors are the unique prime numbers appearing in the prime factorization.

Key Concept

Prime Factorization of an Expression Sum
Estimated Time:1m 30s
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