Why does the divisibility test for 7 work?
Divisibility by 7: The absolute difference between twice the units digit and the number formed by the rest of the digits must be divisible by 7 7 7 (this process can be repeated for many times until we arrive at a sufficiently small number).
Who discovered divisibility rule of 7?
Chika Ofili
About Chika’s discovery A 12-year old Nigerian boy, Chika Ofili, made history this year after his new discovery in the field of mathematics. He was awarded at the TruLittle Hero Awards for discovering the new divisibility test of 7, popularly called as Chika’s Test.
How do you prove multiples of 7?
How to Tell if a Number is Divisible by 7
- Take the last digit of the number you’re testing and double it.
- Subtract this number from the rest of the digits in the original number.
- If this new number is either 0 or if it’s a number that’s divisible by 7, then you know that the original number is also divisible by 7.
What is the divisibility rule of 7 with example?
Divisibility rules for numbers 1–30
| Divisor | Divisibility condition | Examples |
|---|---|---|
| 7 | Subtracting 2 times the last digit from the rest gives a multiple of 7. (Works because 21 is divisible by 7.) | 483: 48 − (3 × 2) = 42 = 7 × 6. |
| Subtracting 9 times the last digit from the rest gives a multiple of 7. | 483: 48 − (3 × 9) = 21 = 7 × 3. |
How do you find multiples of 7?
How can you apply the divisibility rules in solving real life problems?
Divisibility rules can be used in everyday life. For example, if you’re at a grocery store and you need to find which deal is better by using divisibility rules. Let’s say 2 cans of beans cost Rs. 6 and in another store, 4 cans of beans cost Rs.
What is the seventh multiple of 7?
7 x 1 = 7 so we can say that 7 is a multiple of 7. 7 x 2 = 14 so we can say that 14 is a multiple of 7. 7 x 3 = 21 so we can say that 21 is a multiple of 7….List of the Multiples of 7.
| Multiplication | Multiples of 7 |
|---|---|
| 7 * 9 | 63 |
| 7 * 10 | 70 |
How can I use divisibility rules to show that 343 is divisible by 7?
Example: 123,456 is divisible by 12, since it is divisible by both 3 and 4. (See examples for 3 and 4 above.) Example: 343 is divisible by 7. Since this number, 28, is divisible by 7, (28 ÷ 7 = 4), we know that the original number, 343, is divisible by 7.
How do you use the divisibility rule?
The Divisibility Rules
- Any integer (not a fraction) is divisible by 1.
- The last digit is even (0,2,4,6,8)
- The sum of the digits is divisible by 3.
- The last 2 digits are divisible by 4.
- The last digit is 0 or 5.
- Is even and is divisible by 3 (it passes both the 2 rule and 3 rule above)