https://www.khanacademy.org/math/class-8-tg/xc1c312da8d7d0ce2:playing-with-numbers/xc1c312da8d7d0ce2:puzzles-based-on-divisibility-rules/v/divisibility-sum-and-difference 2026-03-22T06:53:37.482695608Z Divisibility - sum and difference Discover an amazing property of divisibility that will change how you think about numbers! If two numbers are both divisible by the same number, what happens when you add or subtract them? This video unveils a powerful mathematical rule that works every single time. We start with simple examples: 16 and 20 are both divisible by 4, but is their sum also divisible by 4? Follow along as we explore multiple examples and then dive deep into WHY this works. It's all about the power of common factors! Learn how to break down numbers like 16 as 4 × 4 and 20 as 4 × 5, and see how taking the common factor out proves the rule. But that's not all, we also explore what happens with differences. If 35 and 20 are both divisible by 5, is their difference also divisible by 5? The answer might surprise you (or maybe not, once you understand common factors!). Perfect for Class 6 students learning about factors, multiples, and divisibility properties. This video makes a complex concept crystal clear with step-by-step breakdowns and multiple examples. Khan Academy video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Divisibility - sum and difference Discover an amazing property of divisibility that will change how you think about numbers! If two numbers are both divisible by the same number, what happens when you add or subtract them? This video unveils a powerful mathematical rule that works every single time. We start with simple examples: 16 and 20 are both divisible by 4, but is their sum also divisible by 4? Follow along as we explore multiple examples and then dive deep into WHY this works. It's all about the power of common factors! Learn how to break down numbers like 16 as 4 × 4 and 20 as 4 × 5, and see how taking the common factor out proves the rule. But that's not all, we also explore what happens with differences. If 35 and 20 are both divisible by 5, is their difference also divisible by 5? The answer might surprise you (or maybe not, once you understand common factors!). Perfect for Class 6 students learning about factors, multiples, and divisibility properties. This video makes a complex concept crystal clear with step-by-step breakdowns and multiple examples. 440 Puzzles based on divisibility rules https://www.khanacademy.org/math/class-8-tg/xc1c312da8d7d0ce2:playing-with-numbers/xc1c312da8d7d0ce2:puzzles-based-on-divisibility-rules/e/divisibility-of-sum-difference-of-two-numbers 2026-03-22T06:53:37.482695608Z Divisibility of sum/difference of two numbers In this exercise we will learn, (a) If two given numbers are divisible by a number, then their sum is also divisible by that number. (b) If two given numbers are divisible by a number, then their difference is also divisible by that number. Khan Academy exercise https://www.khanacademy.org/math/revision-tg-math-class-8/x9ce0e841a99d4a8a:week-3/x9ce0e841a99d4a8a:playing-with-numbers/v/a-divisible-b-a-is-divisible-by-factor-of-b 2026-03-22T06:53:37.482695608Z a divisible b, a is divisible by factor of b Master the key divisibility rules you need to know! This video breaks down what happens when a number is divisible by another number and introduces the concept of co-primes. We'll start by exploring factors and divisibility through clear examples with 24 and 36, then discover an important pattern: **if A is divisible by B, then A is divisible by all factors of B**. Next, we'll introduce co-primes and learn when two numbers can be multiplied together to determine divisibility. You'll see this rule in action through concrete examples like 80 (divisible by 4 and 5) and 60 (divisible by 3 and 5). We'll also cover the critical warning: this rule only works when the numbers are co-primes! Learn why 12, 4, and 6 break the pattern and understand the mathematical reasoning behind each rule. Khan Academy video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw a divisible b, a is divisible by factor of b Master the key divisibility rules you need to know! This video breaks down what happens when a number is divisible by another number and introduces the concept of co-primes. We'll start by exploring factors and divisibility through clear examples with 24 and 36, then discover an important pattern: **if A is divisible by B, then A is divisible by all factors of B**. Next, we'll introduce co-primes and learn when two numbers can be multiplied together to determine divisibility. You'll see this rule in action through concrete examples like 80 (divisible by 4 and 5) and 60 (divisible by 3 and 5). We'll also cover the critical warning: this rule only works when the numbers are co-primes! Learn why 12, 4, and 6 break the pattern and understand the mathematical reasoning behind each rule. 370 Puzzles based on divisibility rules https://www.khanacademy.org/math/class-8-tg/xc1c312da8d7d0ce2:playing-with-numbers/xc1c312da8d7d0ce2:puzzles-based-on-divisibility-rules/e/if-a-is-divisible-b-then-a-is-divisible-by-each-factor-of-b 2026-03-22T06:53:37.482695608Z If 'a' is divisible 'b', then 'a' is divisible by each factor of 'b'. In this exercise we learn the following concepts, (i) If a number ‘a’ is divisible by another number ‘b’, then it is divisible by each of the factors of that number ‘b’. (ii) If ‘ a’ and ‘b’ have no common factors (other than unity), the number divisible by ‘a’ and ‘b’ is also divisible by a × b. Khan Academy exercise https://www.khanacademy.org/math/class-8-tg/xc1c312da8d7d0ce2:playing-with-numbers/xc1c312da8d7d0ce2:puzzles-based-on-divisibility-rules/v/divisibility-by-7 2025-10-27T11:00:46.958143659Z Divisibility by 7 In this video, learn the divisibility rule for 7 and how to apply it to both 3-digit numbers and larger numbers. We’ll go step by step through examples to see how the rule works and why it helps us quickly check if a number is divisible by 7—without actual division Courses on Khan Academy are always 100% free. Start practicing—and saving your progress—now!Unit link 00:00 Rule for divisibility of any three digit number by 7 03:13 Example 04:20 Divisibility of a large number by 7 Khan Academy India is a nonprofit organization with the mission of providing a free, world-class education for anyone, anywhere. We have videos and exercises that have been translated into multiple Indian languages, and 15 million people around the globe learn on Khan Academy every month. Support Us: https://india.khanacademy.org/donate Created by Khan Academy Khan Academy video https://cdn.kastatic.org/googleusercontent/ZCdwTudJg6e6n-P2gsaUborP4izvMsGo71pvEVlX9dNYWcLXcP7VHkWpn2grt4TUP1KoJLQP9NswyHBuBLSFTBw Divisibility by 7 In this video, learn the divisibility rule for 7 and how to apply it to both 3-digit numbers and larger numbers. We’ll go step by step through examples to see how the rule works and why it helps us quickly check if a number is divisible by 7—without actual division Courses on Khan Academy are always 100% free. Start practicing—and saving your progress—now!Unit link 00:00 Rule for divisibility of any three digit number by 7 03:13 Example 04:20 Divisibility of a large number by 7 Khan Academy India is a nonprofit organization with the mission of providing a free, world-class education for anyone, anywhere. We have videos and exercises that have been translated into multiple Indian languages, and 15 million people around the globe learn on Khan Academy every month. Support Us: https://india.khanacademy.org/donate Created by Khan Academy https://cdn.kastatic.org/ka-youtube-converted/sPw5GrHu9aM.mp4/sPw5GrHu9aM.mp4 395 Puzzles based on divisibility rules