Divisibility Rules and Concepts

The video tutorial covers divisibility tests for numbers, focusing on rules for 2, 4, 5, 8, 10, 3, and 9. It explains how to determine if a number is divisible by these numbers using specific rules, such as checking the last digit or the sum of digits. The tutorial includes examples and exercises to apply these rules, emphasizing the importance of understanding these concepts for homework and exams.

Which of the following numbers is a factor of 32?

• 2

• 5

• 7

• 9

What is the rule for determining if a number is divisible by 4?

• The number is even

• The sum of the digits is divisible by 4

• The last two digits form a number divisible by 4

• The last digit is 0 or 5

How can you tell if a number is divisible by 8?

• The last digit is 8

• The number ends in 0

• The last three digits form a number divisible by 8

• The sum of the digits is divisible by 8

What do the numbers 12, 18, 30, 66, and 93 have in common?

• They are all even numbers

• They are all divisible by 3

• They are all prime numbers

• They are all greater than 100

If the sum of a number's digits is divisible by 9, what can be said about the number?

• It is divisible by 3

• It is an even number

• It is a prime number

• It is divisible by 9

Which of the following numbers is divisible by both 3 and 9?

• 54

• 45

• 81

• 27

What is the sum of the digits of 765, and is it divisible by 3?

• 21, No

• 18, Yes

• 18, No

• 21, Yes

If a number is divisible by 9, what else can be said about it?

• It is also divisible by 3

• It is an odd number

• It is less than 100

• It is a prime number

Which of the following numbers is not divisible by 3?

• 22

• 15

• 12

• 30

What is the purpose of using divisibility rules?

• To calculate square roots

• To find prime numbers

• To avoid long division

• To determine even numbers