Divisibility and Digit Sums

In this video, Mr. J explains the divisibility rule for 3, which involves checking if the sum of a number's digits is divisible by 3. He demonstrates this rule with four examples: 72, 5325, 278923, and 9364080. For each number, he calculates the sum of the digits and checks if the sum is divisible by 3, concluding whether the original number is divisible by 3. The video ends with a summary of the rule and a thank you to the viewers.

What is the main purpose of checking divisibility?

• To find the largest number

• To find the smallest number

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

• To determine if a number is even

What is the first step in checking if a number is divisible by three?

• Multiply the digits

• Subtract the digits

• Add the digits

• Divide the digits

What is the sum of the digits of 72?

• 5

• 9

• 7

• 12

Is the number 72 divisible by three?

• Only if it's even

• No

• Only if it's odd

• Yes

What is the sum of the digits of 5325?

• 10

• 12

• 18

• 15

Is the number 5325 divisible by three?

• No

• Yes

• Only if it's odd

• Only if it's even

What is the sum of the digits of 278,923?

• 31

• 28

• 35

• 33

Is the number 278,923 divisible by three?

• Yes

• Only if it's even

• No

• Only if it's odd

What is the sum of the digits of 9,364,080?

• 28

• 25

• 30

• 32

Is the number 9,364,080 divisible by three?

• Only if it's odd

• Yes

• No

• Only if it's even