Write the greatest factor of the following numbers (except for the number itself)
`42`

Options

A. `21`
B. `42`
C. `12`
D. `20`

Answer

To find the greatest factor of the number 42, except for the number itself, we can follow these steps:

### Step-by-Step Solution:

1. **Understand what a factor is**: A factor of a number is any number that divides that number completely without leaving a remainder.

2. **List the factors of 42**: We will find all the numbers that can divide 42 completely.
- Start with 1: \( 42 \div 1 = 42 \) (1 is a factor)
- Next, check 2: \( 42 \div 2 = 21 \) (2 is a factor)
- Then check 3: \( 42 \div 3 = 14 \) (3 is a factor)
- Next, check 6: \( 42 \div 6 = 7 \) (6 is a factor)
- Check 7: \( 42 \div 7 = 6 \) (7 is a factor)
- Check 14: \( 42 \div 14 = 3 \) (14 is a factor)
- Check 21: \( 42 \div 21 = 2 \) (21 is a factor)
- Finally, check 42: \( 42 \div 42 = 1 \) (42 is a factor, but we will exclude it)

3. **List of factors**: The complete list of factors of 42 is: 1, 2, 3, 6, 7, 14, 21, and 42.

4. **Identify the greatest factor excluding 42**: From the list of factors, we need to find the greatest one excluding 42 itself. The factors we have are: 1, 2, 3, 6, 7, 14, and 21.

5. **Determine the greatest factor**: The largest number from the list excluding 42 is 21.

### Final Answer:
The greatest factor of 42, except for the number itself, is **21**.

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