Question
(4)) Which is a composite number? \( \begin{array}{llll}\text { (4)) } 21 & \text { (4)) } 29 & \text { (f) } 23 & 43\end{array} \)
Ask by Burgess Lyons. in the United States
Mar 11,2025
Upstudy AI Solution
Tutor-Verified Answer
Answer
21 is a composite number.
Solution
To determine which of the given numbers is a composite number, we first need to understand the definitions:
- A **composite number** is a positive integer that has at least one positive divisor other than one or itself. In other words, it can be divided evenly by numbers other than 1 and itself.
- A **prime number** is a positive integer greater than 1 that has no positive divisors other than 1 and itself.
Now, let's analyze each of the given numbers:
1. **21**:
- Divisors: 1, 3, 7, 21
- Since it has divisors other than 1 and itself, 21 is a composite number.
2. **29**:
- Divisors: 1, 29
- Since it has no divisors other than 1 and itself, 29 is a prime number.
3. **23**:
- Divisors: 1, 23
- Since it has no divisors other than 1 and itself, 23 is a prime number.
4. **43**:
- Divisors: 1, 43
- Since it has no divisors other than 1 and itself, 43 is a prime number.
From this analysis, the only composite number among the options is **21**.
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Simplify this solution Extra Insights
A composite number is a positive integer that has at least one positive divisor other than one or itself. Among the numbers you provided, 21 is the composite number since it can be divided by 1, 3, 7, and 21. On the other hand, 29, 23, and 43 are prime numbers as they can only be divided by 1 and themselves. To identify composite numbers, always check for factors. Remember, if you can find at least one other factor (other than 1 and the number itself), you've got a composite on your hands! For example, with 21, both 3 and 7 are factors, sealing its composite status.
