Math Problem Statement

a number N is between 2 to the fifth power and 3 to the fourth power . How many possible values of N are there that has even number of factors?

Solution

We are given that a number NN lies between 252^5 and 343^4, and we need to determine how many possible values of NN have an even number of factors.

Step 1: Calculate 252^5 and 343^4

25=322^5 = 32 34=813^4 = 81 So, the number NN lies between 32 and 81.

Step 2: Determine the numbers between 32 and 81

The integers between 32 and 81 are: 33,34,35,,8033, 34, 35, \ldots, 80 These numbers are from 33 to 80, inclusive, which gives us: 8033+1=48 possible values of N.80 - 33 + 1 = 48 \text{ possible values of } N.

Step 3: Determine when a number has an even number of factors

A number has an even number of factors unless it is a perfect square. This is because the factors of a number usually come in pairs (e.g., for 12, the factors are 1×121 \times 12, 2×62 \times 6, 3×43 \times 4), but for a perfect square, one factor is repeated (e.g., for 36, the factors are 1×361 \times 36, 2×182 \times 18, 3×123 \times 12, 4×94 \times 9, 6×66 \times 6).

Step 4: Identify the perfect squares between 32 and 81

We find the perfect squares between 32 and 81: 62=36,72=49,82=64,92=816^2 = 36, \quad 7^2 = 49, \quad 8^2 = 64, \quad 9^2 = 81 So the perfect squares in this range are 36, 49, 64, and 81.

Step 5: Count the numbers with an even number of factors

The total number of integers between 33 and 80 is 48. Out of these, 4 are perfect squares (36, 49, 64, 81), which have an odd number of factors. The remaining numbers will have an even number of factors: 484=4448 - 4 = 44

Final Answer:

There are 44 numbers between 32 and 81 that have an even number of factors.


Would you like further details or have any questions? Here are some related questions:

  1. How do you calculate the number of factors of a given number?
  2. What is the significance of perfect squares in factorization?
  3. Can a number have both an odd and an even number of factors?
  4. How would the answer change if the range for NN was extended?
  5. What is the connection between prime factorization and the number of divisors?

Tip: The number of divisors of a number can be found using its prime factorization!

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Math Problem Analysis

Mathematical Concepts

Number Theory
Factors
Perfect Squares

Formulas

Number of divisors formula: product of (exponents + 1)
Even number of factors unless perfect square

Theorems

Perfect squares have an odd number of factors
Non-perfect squares have even number of factors

Suitable Grade Level

Grades 8-10