Math Problem Statement

How many zeroes are at the end of 45^9 • 88^5? Explain how you can answe this question without actually computing the number.

How many zeroes are at the end of 45^9 • 88^5? Explain how you can answer this question without actually computing the number.

Solution

To determine how many zeros are at the end of the number 459×88545^9 \times 88^5 without actually computing the number, we need to consider the prime factors involved.

Step 1: Prime Factorization

  • Prime factorization of 45: 45=32×545 = 3^2 \times 5 So, 459=(32×5)9=318×5945^9 = (3^2 \times 5)^9 = 3^{18} \times 5^9

  • Prime factorization of 88: 88=23×1188 = 2^3 \times 11 So, 885=(23×11)5=215×11588^5 = (2^3 \times 11)^5 = 2^{15} \times 11^5

Step 2: Combine the Factors

Now, multiply the factorizations: 459×885=(318×59)×(215×115)=215×318×59×11545^9 \times 88^5 = (3^{18} \times 5^9) \times (2^{15} \times 11^5) = 2^{15} \times 3^{18} \times 5^9 \times 11^5

Step 3: Determine the Number of Zeros

The number of zeros at the end of a number is determined by the number of factors of 10 in its factorization. Since 10=2×510 = 2 \times 5, the number of zeros at the end of the product is the minimum of the powers of 2 and 5 in its factorization.

  • The power of 2 in the factorization is 1515.
  • The power of 5 in the factorization is 99.

Conclusion:

The number of zeros at the end of 459×88545^9 \times 88^5 is the minimum of these two, which is 9.

Would you like more details or have any further questions?


Relative Questions:

  1. How would the number of zeros change if we computed 4510×88545^{10} \times 88^5?
  2. What would happen to the number of zeros if the exponents of 45 and 88 were both doubled?
  3. How does prime factorization help in finding the number of zeros in any product?
  4. If you multiply 459×88545^9 \times 88^5 by 10310^3, how many zeros would the result have?
  5. How would you find the number of trailing zeros in n!n! for any positive integer nn?

Tip: When calculating the number of trailing zeros in a product or factorial, always focus on the factors of 2 and 5, as these together make a 10.

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Math Problem Analysis

Mathematical Concepts

Prime Factorization
Exponents
Trailing Zeros

Formulas

Prime factorization: a = p1^k1 * p2^k2 * ... * pn^kn
Counting trailing zeros: number of zeros = min(count of 2's, count of 5's)

Theorems

Fundamental Theorem of Arithmetic

Suitable Grade Level

Grades 10-12