Divisibility rules
Is 3,462 divisible by 9? You do not need to divide: add the digits (3 + 4 + 6 + 2 = 15) and ask the same question of 15. Divisibility rules let you check in seconds what long division would take a minute to show.
Three lessons cover every rule worth knowing — the last digit (2, 5, 10), the digit sum (3, 9), and the last few digits (4, 8) plus 6 as "2 and 3". Practice asks for the remainder, so a 0 means "yes, it divides".
Divisibility by 2, 5 and 10: Look at the Last Digit
Only the last digit matters: even → divisible by 2; 0 or 5 → by 5; 0 → by 10. The remainder comes from the last digit too: 953 ÷ 10 leaves 3.
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Method 2 · Level 2Divisibility by 3 and 9: Add the Digits
Add the digits. If the sum divides by 3 (or 9), so does the number — and the digit sum leaves the same remainder as the number. For 9, keep adding the digits: 3,462 → 15 → 6, so 3,462 ÷ 9 leaves 6. For 3, divide the sum by 3.
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Method 3 · Level 2Divisibility by 4, 6 and 8
÷4: check the last two digits (7,316 → 16, and 16 ÷ 4 = 4). ÷8: check the last three digits. ÷6: the number must pass both the 2 test and the 3 test.
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