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Grade 9

11.06 Algorithms for divisibility

Worksheet
Algorithms for divisibility
1

To test whether a number is divisible by 10, the following simple algorithm wil be used:

"If the number ends in a 0, then the number is divisible by 10."

Write down all the numbers from the following lists that are divisible by 10.

a

313, \, 882, \, 710, \, 170, 479,\, 381,\, 860,\, 465, \, 256,\, 344

b

42\,381,\, 92\,176,\, 86\,498, \, 59\,433,\, 24\,499, \, 21\,880, \, 95\,534,\, 61\,110,\, 25\,190, \, 39\,137

c

6\,459\,620,\, 5\,638\,943, \,2\,878\,605,\, 1\,904\,790, \,5\,037\,628, \,6\,805\,217

2

To test whether a number is divisible by 2, the following simple algorithm will be used:

"If the number is even (that is, the digit in the ones column is even), then the number is divisible by 2."

Write down all the numbers from the following lists that are divisible by 2.

a

63, \,35, \,16, \,43, \,71, \,11,\, 97, \,80, \,74, \,59

b

391, \,138, \,575, \,385, \,917, \,787,\, 873, \,992, \,239, \,564

c

6\,750\,025, \,4\,415\,417,\, 8\,603\,042, \,3\,789\,901,\, 7\,103\,764, \,2\,670\,389

3

To test whether a number is divisible by 5, the following simple algorithm will be used:

"If the number ends in a 0 or a 5, then the number is divisible by 5."

Write down all the numbers from the following lists that are divisible by 5.

a

85, \,38, \,63, \,35, \,52, \,90,\, 47,\, 76, \,24,\, 99

b

865, \,583, \,324, \,369,\, 766, \,711,\,920, \,507, \,555, \,678

c

8\,927\,050, \,2\,770\,753, \,6\,606\,005,\, 9\,200\,311, \,9\,911\,699, \,7\,548\,014

4

To test whether a number is divisible by 3, the following algorithm will be used:

  • Step 1: Find the sum of the digits of the number.

  • Step 2: If the sum is a multiple of 3, then the number itself is a multiple of 3.

Determine whether the following numbers are divisible by 3.

a

34\,257

b
7\,352\,941
c
946\,357\,246\,188
5

To test whether a number is divisible by 6, the following algorithm will be used:

  • Step 1: Test whether the number is divisible by 2.

  • Step 2: Test whether the number is divisible by 3.

  • Step 3: If the number is divisible by both 2 and 3, then the number is divisible by 6.

Determine whether the following numbers are divisible by 6.

a
42\,765
b
51\,329\,784
c
32\,156\,894
d
943\,162\,547\,886
6

To test whether a number is divisible by 9, the following algorithm will be used:

  • Step 1: Find the sum of the digits of the number.

  • Step 2: If the sum is a multiple of 9, then the number itself is divisible by 9.

Determine whether the following numbers are divisible by 9.

a

49\,536

b
27\,648\,391
c
354\,427\,126\,389
7

To test whether a number is divisible by 4, the following simple algorithm will be used:

"If the last two digits are divisible by 4, then the whole number is divisible by 4."

Write down all the numbers from the following lists that are divisible by 4.

a

8934, \, 6236,\, 5943, \,3130, \,5122, \,2025,\, 1528, \,6632,\, 9217, \,8339

b

1\,805\,159,\, 2\,952\,174,\, 9\,951\,756,\, 5\,885\,468,7\,486\,650, \,1\,581\,254,\,4\,993\,860,\, 4\,924\,944

c

30\,685\,091, \,45\,590\,085,\, 13\,189\,788, \,29\,003\,798, \,81\,339\,993,\, 92\,123\,492

8

To test whether a number is divisible by 8, the following algorithm will be used:

"If the last three digits are divisible by 8, then the whole number is divisible by 8."

Determine whether the following numbers are divisible by 8.

a
42\,344
b
62\,106
9

Consider the following numbers:

940,\quad 257,\quad 8535, \quad486,\quad 1923, \quad11\,705, \quad21\,735,\quad 92\, 872,\quad\\ 98\, 941, \quad77\, 990, \quad2327,\quad 6644,\quad 985,\quad 605,\quad 8470
a

List all the numbers that are divisible by 10.

b

List all the numbers that are divisible by 5.

c

List all the numbers that are divisible by 2.

d

List all the numbers that are divisible by 10, 5 and 2.

10

For each of the following numbers:

i

Determine whether the number is divisible by 2.

ii

Determine whether the number is divisible by 3.

iii

Determine whether the number is divisible by 9.

iv

Hence, determine whether the number is divisible by both 6 and 9.

a
835\,794
b
6\,712\,854
11

To test whether a number is divisible by 7, the following algorithm will be used:

  • Step 1: Remove the last digit and double it.

  • Step 2: Subtract this answer from the remaining digits.

  • Step 3 (Optional): Repeat Step 1 and Step 2 until the number is small enough for you to confidently divide by 7.

  • Step 4: It the final answer is divisible by 7, then the whole number is divisible by 7.

Determine whether the following numbers are divisible by 7.

a
3185
b
1789
12

To test whether a number is divisible by 11, the following algorithm will be used:

  • Step 1: Remove the last digit and subtract it from the remaining digits.

  • Step 2 (Optional): Repeat Step 1 until the number is small enough for you to confidently divide by 11.

  • Step 3: If the final answer is divisible by 11, then the whole number is divisible by 11.

Determine whether the following numbers are divisible by 11.

a
2948
b
2974
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Outcomes

9.C2.1

Use coding to demonstrate an understanding of algebraic concepts including variables, parameters, equations, and inequalities.

9.C2.2

Create code by decomposing situations into computational steps in order to represent mathematical concepts and relationships, and to solve problems.

9.C2.3

Read code to predict its outcome, and alter code to adjust constraints, parameters, and outcomes to represent a similar or new mathematical situation.

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