Divisibility
Divisibility rules help us quickly determine if a number can be evenly divided by another number, without doing long division.
Core concept
A number is divisible by 2 if its last digit is even (0,2,4,6,8), and divisible by 5 if it ends in 0 or 5.
How it works
A number is divisible by 3 if the sum of its digits is divisible by 3, and divisible by 9 if the digit sum is divisible by 9.
Why it matters
A number is divisible by 10 if it ends in 0, and divisible by 4 if its last two digits form a number divisible by 4.
Key detail
Understanding divisibility rules helps us quickly simplify fractions, find factors, and solve problems without long division.
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Quick notes
• Divisible by 2: last digit even.
• Divisible by 5: ends in 0 or 5.
• Divisible by 3: digit sum divisible by 3.
• Divisible by 9: digit sum divisible by 9.
• Divisible by 10: ends in 0.
• Divisible by 4: last two digits divisible by 4.
• Rules avoid long division.
• They help simplify fractions, find factors.