Lesson 5 of 9
Quick tests without dividing
Show on a big screenIs 2 a factor of 348? Look at the last digit, 8. Yes. A digit is one of 0 to 9. 348 has digits 3, 4 and 8.
Step 1 of 4
- The number 348, digit by digit.
- Last digit 8 is even → 2 fits.
- Add every digit: 3 + 4 + 8 = 15.
- 15 is a multiple of 3 → 3 fits.
The rule
A divisibility rule checks part of a number, not all of it. The divisor is the number you divide by. The digit sum is all the digits added: 3 + 4 + 8 = 15.
| Divisor | Rule | Example |
|---|---|---|
| 2 | Last digit even (0, 2, 4, 6, 8) | 348 → 8 → yes |
| 5 | Last digit 0 or 5 | 345 → 5 → yes |
| 10 | Last digit 0 | 340 → 0 → yes |
| 3 | Digit sum is a multiple of 3 | 348 → 15 → yes |
| 4 | Last two digits make a multiple of 4 | 316 → 16 → yes |
| 6 | Fits both 2 and 3 | 714 → even, sum 12 → yes |
| 9 | Digit sum is a multiple of 9 | 348 → 15 → no |
A rule always agrees with dividing. 348 ÷ 3 = 116 exactly. Check: 3 × 116 = 348.
Answer each question in the lab. Use the quick test.
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Try the lab to finish this lesson.