Divisibility Rules and Digit Sums

This video tutorial by Mr. J explains the divisibility rule for 9, which states that a number is divisible by 9 if the sum of its digits is divisible by 9. The video provides four examples to illustrate this rule: 918, 33,502, 9,890,550, and 4,607,928. Each example demonstrates how to calculate the sum of the digits and check for divisibility by 9. The video concludes with a summary of the rule, emphasizing its simplicity and utility in determining divisibility.

What is the main purpose of checking divisibility?

• To find the sum of the digits

• To determine if a number can be divided without a remainder

• To multiply the digits

• To subtract the digits

According to the divisibility rule for nine, what must be true for a number to be divisible by 9?

• The number must end in 9

• The number must be even

• The sum of its digits must be divisible by 9

• The number must be a multiple of 3

What is the sum of the digits of 918?

• 22

• 20

• 18

• 16

Is the number 918 divisible by 9?

• No, because 18 divided by 9 is 1

• Yes, because 18 divided by 9 is 2

• No, because 18 divided by 9 is not an integer

• Yes, because 18 divided by 9 is 3

What is the sum of the digits of 33,502?

• 17

• 11

• 13

• 15

Is the number 33,502 divisible by 9?

• Yes, because 13 divided by 9 is an integer

• No, because 13 divided by 9 is not an integer

• Yes, because 13 divided by 9 is 2

• No, because 13 divided by 9 is 1

What is the sum of the digits of 9,890,550?

• 37

• 36

• 35

• 34

Is the number 9,890,550 divisible by 9?

• Yes, because 36 divided by 9 is 4

• No, because 36 divided by 9 is not an integer

• Yes, because 36 divided by 9 is 3

• No, because 36 divided by 9 is 1

What is the sum of the digits of 4,607,928?

• 36

• 35

• 37

• 34

Is the number 4,607,928 divisible by 9?

• No, because 36 divided by 9 is 1

• Yes, because 36 divided by 9 is 3

• No, because 36 divided by 9 is not an integer

• Yes, because 36 divided by 9 is 4