Comprehensive Calculator Guide
This calculator tests your number against 2 to 12, applying each rule to your digits: the last digit for 2, 5 and 10, the digit sum for 3 and 9, the last two and three digits for 4 and 8, and the rules for 7 and 11. 2520 divides by every number from 2 to 12 except 11.
The rules
2: even last digit. 3 and 9: digit sum. 4 and 8: last two or three digits. 5 and 10: last digit. 6 and 12: combine two rules. 7: subtract twice the last digit from the rest. 11: alternating digit sum.
How to Use
- Enter the number.
- It is tested against 2 to 12.
- Press “Test” to see which divide it and each rule applied.
Formula Used
2: last digit even; 3: digit sum; 5: last digit 0 or 5; 9: digit sum…
Practical Examples
- Example 1
- 2520: all but 11.
- Example 2
- 1001: 7 and 11.
- Example 3
- 123456: 2, 3, 4, 6, 8, 12.
Important Tips
- Start with 2, 5, 10.
- Combine rules for 6 and 12.
- Use them to simplify fractions.
Common Mistakes to Avoid
- Using only the last digit for 4.
- Assuming 2 and 4 give 8.
- Using digit sums for 6 or 7.
Frequently Asked Questions
- Divisible by 4?
- If the last two digits are.
- Rule for 7?
- Subtract twice the last digit from the rest.
- 2520 and 1–10?
- Divisible by all; the smallest such number.