Divisibility Rules for Number 3

The video tutorial explains how to quickly determine if a number is divisible by 3 by adding its digits and checking if the sum is a multiple of 3. It provides examples with numbers 4792 and 386,802, demonstrating the method. The tutorial then delves into the reasoning behind the rule, using the number 498 to illustrate how each digit's place value contributes to the overall divisibility. The explanation highlights that numbers like 99, 999, etc., are divisible by 3, which supports the rule's validity.

What is the first step to determine if a number is divisible by 3?

• Multiply all the digits together

• Divide the number by 2

• Add up all the digits

• Subtract the smallest digit from the largest

If the sum of the digits of a number is 22, is the number divisible by 3?

• Yes, because 22 is a multiple of 3

• No, because 22 is not a multiple of 3

• Yes, because 22 is an even number

• No, because 22 is a prime number

Why is the number 386,802 divisible by 3?

• Because it is a large number

• Because the sum of its digits is 27, which is divisible by 3

• Because it is a prime number

• Because it ends with an even number

What is the significance of the number 99 in the explanation of divisibility?

• It is the sum of the digits

• It is a prime number

• It is used to demonstrate multiplication

• It is divisible by 3

How can the number 498 be rewritten to explain divisibility by 3?

• As 4 times 100 plus 9 times 10 plus 8

• As 4 times 99 plus 9 times 9 plus 8

• As 4 times 10 plus 9 times 10 plus 8

• As 4 times 1 plus 9 times 1 plus 8

What does the digit 9 in the tens place represent in the number 498?

• 9 times 10

• 9 times 99

• 9 times 1

• 9 times 100

Why is it important to consider the sum of the digits in a number?

• To determine if the number is even

• To check if the number is a prime

• To determine if the number is divisible by 3

• To find the average of the digits

What is the final step to confirm if a number is divisible by 3?

• Subtract the digits from each other

• Multiply the digits together

• Divide the number by 3

• Check if the sum of the digits is a multiple of 3

What is the role of the number 999 in the explanation?

• It is the sum of the digits

• It is a prime number

• It is used to demonstrate addition

• It is divisible by 3

What must be true for a number to be divisible by 3?

• The number must be even

• The sum of its digits must be divisible by 3

• The number must be a multiple of 10

• The number must end in 0