Chapter 1: Problem 10
Label each of the following numbers as prime, composite, or neither. $$15$$
Short Answer
Expert verified
15 is a composite number.
Step by step solution
01
- Understand Definitions
Understand the definitions of prime, composite, and neither: A prime number has exactly two distinct positive divisors, 1 and itself. A composite number has more than two distinct positive divisors. 'Neither' applies to numbers like 1, which do not meet the criteria for prime or composite.
02
- Analyze the Number 15
Identify the factors of the number 15. To do this, determine which numbers divide 15 without leaving a remainder.
03
- Find Divisors
List all the divisors: 1, 3, 5, and 15.
04
- Classify the Number
Since the number 15 has more than two distinct positive divisors (1, 3, 5, and 15), it qualifies as a composite number.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Prime Numbers
Prime numbers are fascinating elements in the realm of mathematics. A number is considered prime if it has exactly two distinct positive divisors: 1 and itself. This means that no other numbers can divide a prime number without leaving a remainder. For example, the number 7 is prime because it can only be divided by 1 and 7. Let's review more examples to solidify our understanding:
- 3 (divisors: 1 and 3)
- 11 (divisors: 1 and 11)
- 23 (divisors: 1 and 23)
Composite Numbers
Understanding composite numbers is equally important. A composite number has more than two distinct positive divisors. This means that, apart from 1 and itself, other numbers can also divide it without leaving a remainder. To identify a composite number, check if it can be divided evenly by any number other than 1 and itself. For instance, the number 15 is composite because it has four divisors: 1, 3, 5, and 15. Other examples include:
- 4 (divisors: 1, 2, and 4)
- 12 (divisors: 1, 2, 3, 4, 6, and 12)
- 20 (divisors: 1, 2, 4, 5, 10, and 20)
Number Divisors
Number divisors are at the heart of understanding both prime and composite numbers. A divisor, or factor, of a number divides that number without leaving a remainder. For example, the divisors of 15 are 1, 3, 5, and 15. This concept is crucial in many areas of mathematics, including simplifying expressions and solving equations. Here's a step-by-step approach to finding divisors:
- Start with 1 and the number itself (these are always divisors)
- Check smaller numbers to see if they divide evenly
- Continue this process up to the square root of the number
Factorization
Factorization is the process of breaking down a number into its prime factors. This is an essential skill in mathematics, as it simplifies many complex problems. For instance, factorizing 15 results in 3 and 5 because 15 = 3 × 5. To factorize a number, follow these steps:
60 ÷ 2 = 30
30 ÷ 2 = 15
15 ÷ 3 = 5
5 ÷ 5 = 1.
Thus, the prime factors of 60 are 2, 2, 3, and 5. Mastering factorization will boost your problem-solving skills in algebra, number theory, and beyond.
- Start by dividing the number by the smallest prime (2, 3, 5, etc.)
- Continue dividing the quotient by prime numbers until you reach 1
- List all the prime numbers used as factors
60 ÷ 2 = 30
30 ÷ 2 = 15
15 ÷ 3 = 5
5 ÷ 5 = 1.
Thus, the prime factors of 60 are 2, 2, 3, and 5. Mastering factorization will boost your problem-solving skills in algebra, number theory, and beyond.