1 / 27

Divisibility tests

Divisibility tests. These are simple tricks to test what a number can be shared by . We are going to learn tricks for testing if a number can be shared by 2, 3, 4, 5, 6, 8, 9, and multiples of 10. New Now with test for divisibility by 7!. Divisibility tests.

thu
Download Presentation

Divisibility tests

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Divisibility tests These are simple tricks to test what a number can be shared by . We are going to learn tricks for testing if a number can be shared by 2, 3, 4, 5, 6, 8, 9, and multiples of 10. New Now with test for divisibility by 7!

  2. Divisibility tests This is a typical SATs question that can be solved by divisibility tests. x x = 150 Here we are asked to list 3 numbers that can be multiplied to make 150. Think about it. We will come back to this question after we learn our skills.

  3. Divisibility tests Divisible by 2? If a number is divisible by 2… It ends with 2, 4, 6, 8, or 0 (in other words it’s an EVEN number.)

  4. Divisibility tests Divisible by 3? If a number is divisible by 3… It’s digit sum is 3, 6, or 9. The digit sum is when you add the digits in the number repeating until you get to 1 digit.

  5. Divisibility tests Divisible by 3? So the number 1467 has a digit sum of 9 1 + 4 + 6 + 7 = 18 then 1 + 8 = 9 So 1467 is divisible by 3.

  6. Divisibility tests Divisible by 4? If a number is divisible by 4… If we half the number, and the result is even, then our number is divisible by 4.

  7. Divisibility tests Divisible by 4? If a number is divisible by 4… If the last 2 digits of a number are divisible by 4, then our number is as well. 4 655 728 is divisible by 4 because 28 is divisible by 4.

  8. Divisibility tests Divisible by 5? If a number is divisible by 5… It ends with a 5 or a 0. 5, 10, 15, 20, 25, 30, …

  9. Divisibility tests Divisible by 6? If a number is divisible by 6… It passes the tests for both divisibility by 2 and divisibility by 3. In other words – an EVEN number with digit sum 3, 6 or 9

  10. Divisibility tests Divisible by 7? If a number is divisible by 7… Double the last digit, and subtract it from the rest of the number. If the result is divisible by 7 then the original number is. Repeat process if need be!

  11. Divisible by 7? Double the last digit and subtract from the rest. 357 35 – (2x7) = 35 – 14 = 21 So 357 is divisible by 7 4434 442-(4x2) = 442 – 8 = 434 = 43-8=35 So 4434 is divisible by 7 because 35 is. 813 81 – 6 = 75 Not divisible by 7 because 75 isn’t.

  12. Divisibility tests Divisible by 8? If a number is divisible by 8… If you halve it, and halve it again, the result is an even number. If the last 3 digits are divisible by 8, the whole number will be.

  13. Divisibility tests Divisible by 8? If a number is divisible by 8… So 2, 560, 104 is divisible by 8 because 104 is divisible by 8. ( 104 ÷ 2 = 52 52 ÷ 2 = 26 26 is EVEN. )

  14. Divisibility tests Divisible by 9? If a number is divisible by 9… It’s digit sum is 9 This means it is also divisible by 3!

  15. Divisibility tests Divisible by 10? If a number is divisible by 10… It ends in a 0 So these numbers are also divisible by 2 and 5

  16. Divisibility tests Divisible by 100? If a number is divisible by 100… It ends in a 00

  17. Divisibility tests Divisible by 1000? If a number is divisible by 1000… It ends in a 000 And so on…

  18. Divisibility tests Divisible by …? 2: ends with 2, 4, 6, 8, or 0 3: digit sum is 3, 6, or 9 4: halve last 2 digits and the result is even 5: ends with 5 or 0 6: ends with 2, 4, 6, 8, or 0 AND digit sum is 3, 6, or 9 7: - 8: Halve the last 3 digits twice, and the result is even. 9: digit sum is 9 10: ends with 0

  19. Divisibility tests Remember this question… x x = 150 Test 150 to see what can go in the boxes.

  20. Divisibility tests Remember this question… x x = 150 150 is divisible by 2, 3, 5, 6, and 10 amongst other numbers (pick any one for the first box)

  21. Divisibility tests Remember this question… 2 x x = 150 150 ÷ 2 = 75

  22. Divisibility tests Remember this question… 2 x x = 150 These must multiply to make 75

  23. Divisibility tests Remember this question… 2 x x = 150 Test 75 for divisibility

  24. Divisibility tests Remember this question… 2 x x = 150 75 is divisible by 3 and 5 among others (pick either for second box).

  25. Divisibility tests Remember this question… 2 x 3 x = 150 75 ÷ 3 = 25

  26. Divisibility tests Remember this question… 2 x 3 x 25 = 150 This is one solution. Can you think of others?

  27. Divisibility tests Let’s try a similar question. x x = 15.0

More Related