# Divisibility Rules One number is divisible by another

Divisibility Rules One number is divisible by another number when it can divide into it without a remainder. Ex. 56 is divisible by 7 because it goes into 56 exactly 8 times.

§ The following number is divisible by (2, 3, 5, 6, 9, 10). Why? What do you think are the rules? § 492, 570

Rule for 2. . . A number is divisible by 2 if the last digit (ones place) is an even number (0, 2, 4, 6, 8) Ex. 3, 978 Not an example: 4, 975

Rule for 3. . . A number is divisible by 3 if the sum of the digits is divisible by 3. Ex. 315 b/c 3 + 1 + 5 = 9 and 3 goes into 9 Not an example: 139 b/c 1 + 3 + 9 = 13 and 3 does not go into 13

Rule for 4. . . A number is divisible by 4 if the last two digits form a number divisible by 4. Ex. 8, 512 12 makes up the last two digits and 4 goes into 12 Not an example: 7, 518 into 18 4 does not go

Rule for 5. . . A number is divisible by 5 if the last digit (ones place) is a 0 or 5. Ex. 14, 975 Not an example: 10, 978

Rule for 6. . . A number is divisible by 6 if the number is divisible by BOTH 2 and 3. Ex. 48 is divisible by 2 and 3 so it is divisible by 6 Not an example: 20 is divisible by 2 but not 3 so it’s not divisible by 6

Rule for 8. . . A number is divisible by 8 if the last three digits is divisible by 8. Ex. 2848 is divisible by 8 b/c 848 is divisible by 8 Not an example: 32, 850 is not divisible by 8 b/c 8 does not go into 850

Rule for 9. . . A number is divisible by 9 if the sum of the digits is divisible by 9. Ex. 711 b/c 7 + 1 = 9 and 9 goes into 9 Not an example: 93 b/c 9 + 3 = 12 and 9 does not go into 12

Rule for 10. . . A number is divisible by 10 when the last digit (ones place) is a 0. Ex. 15, 990 Not an example: 10, 535

Examples to try Tell whether each number is divisible by 2, 3, 4, 5, 6, 8, 9, or 10. 1. 565 2. 2, 340 3. 95, 994 4. 43 5. 1800

Answers 1. 2. 3. 4. 5. 5 2, 3, 4, 5, 6, 9, 10 2, 3, 6, 9 None 2, 3, 4, 5, 6, 8, 9, 10

Homework “Some Friendly Advice” worksheet

- Slides: 13