Divisibility and Mental Math Rules Explained
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Learn about divisibility rules and mental math techniques to determine if a number is divisible by another. Discover how to apply rules for 2, 3, 5, 9, and 10 to identify factors. Practice examples included for better understanding.
Divisibility and Mental Math Rules Explained
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Presentation Transcript
Vocabulary A number is divisible by another number if it can be divided into and result in a remainder of 0. 24 is divisible by 4, because 24 ÷ 4 = 6. 24 is not divisible by 5, because 24 ÷ 5 = 4.8 (or 4R4). An even number ends with a 0, 2, 4, 6, or 8. An odd number ends with a 1, 3, 5, 7, or 9.
Divisibility Rules 2 divides into all even numbers. 3 divides into a number if the sum of the digits of that number is divisible by 3. 5 divides into numbers that end with a 5 or 0. 9 divides into a number if the sum of the digits of that number is divisible by 9. 10 divides into numbers that end with 0.
Example: Test each number for divisibility by 3. 216 2 + 1 + 6 = 9 9 is divisible by 3, so 216 is divisible by 3. yes 437 4 + 3 + 7 = 14 14 is not divisible by 3, so 437 is not divisible by 3. no
Example: Test the number for divisibility by 2, 5, or 10. 454,320 2 works because the number is even. 5 works because the number ends with 0. 10 works because the number ends with 0. 4 + 5 + 4 + 3 + 2 + 0 = 18. Is the number divisible by 9? 18 is divisible by 9, so 454,320 is also divisible by 9.