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Welcome to our Math lesson on Divisibility by 20, this is the twentieth lesson of our suite of math lessons covering the topic of Divisibility Rules, you can find links to the other lessons within this tutorial and access additional Math learning resources below this lesson.
Divisibility by 20
Rule: "A number is divisible by 20 if it ends with zero and the tens digit is even." In other words, a number is divisible by 20 if the number formed by its last two digits is a multiple of 20 (including 0).
For example, 102,480 is divisible by 20 as 80 is divisible by 20 (80 ÷ 20 = 4), while 4790 is not divisible by 20 as 90 ÷ 20 = 4.5.
The calculator confirms our results as 102,480 ÷ 20 = 5124 and 4790 ÷ 20 = 239.5.
Example 4
Check whether the following numbers are divisible by 16, 17, 18, 19 and 20 or not.
- 930,240
- 18,504
Solution 4
- Let's check the divisibility by 16 of 930,240. The last 3 digits form a number divisible by 16 as 240 ÷ 16 = 15, while the fourth digit from the right is even (0 is even number). Hence, 930,240 is divisible by 16.
As for the divisibility by 17, we have 93,024 - 5 × 0 = 93,024; then 9302 - 5 × 4 = 9282; then 928 - 5 × 2 = 918; then 91 - 5 × 8 = 51, which is a number divisible by 17, as 51 ÷ 17 = 3.
The number 930,240 is divisible by 18 as it is even (is divisible by 2 therefore) and the sum of digits is a number divisible by 9 (9 + 3 + 2 + 4 = 18 ÷ 9 = 2).
As for the divisibility by 19, we have 2 × 0 + 93,024 = 93,024; then 2 × 4 + 9302 = 9310; then 2 × 0 + 931 = 931; then 2 × 1 + 93 = 95. This number is divisible by 19 as 95 ÷ 19 = 5.
930,240 is divisible by 20 as its last two digits form a number divisible by 20 (40 ÷ 20 = 2). - 18,504 is not divisible by 16 as 504 ÷ 16 = 31.5. Hence, the last three digits form a number that is not divisible by 16, despite the fourth number from the right is even (8).
18,504 is not divisible by 17 as 1850 - 5 × 4 = 1830; then 183 - 5 × 0 = 183; then 18 - 5 × 3 = 3, which is not a number divisible by 17.
18,504 is divisible by 18 as it is even (divisible by 2 therefore), and the sum of digits is divisible by 9 (1 + 8 + 5 + 0 + 4 = 18 ÷ 9 = 2).
18,504 is not divisible by 19 as 2 × 9 + 1850 = 1868; then 2 × 8 + 186 = 202; then 2 × 2 + 20 = 24, which is not divisible by 19.
The number 18,504 is not divisible by 20 as the number formed by its last two digits (04) is not divisible by 20.
More Divisibility Rules Lessons and Learning Resources
Arithmetic Learning Material| Tutorial ID | Math Tutorial Title | Tutorial | Video
Tutorial | Revision
Notes | Revision
Questions |
|---|
| .6 | Divisibility Rules | | | | |
| Lesson ID | Math Lesson Title | Lesson | Video
Lesson |
|---|
| 1.6.1 | Divisibility by 1 | | |
| 1.6.2 | Divisibility by 2 | | |
| 1.6.3 | Divisibility by 3 | | |
| 1.6.4 | Divisibility by 4 | | |
| 1.6.5 | Divisibility by 5 | | |
| 1.6.6 | Divisibility by 6 | | |
| 1.6.7 | Divisibility by 7 | | |
| 1.6.8 | Divisibility by 8 | | |
| 1.6.9 | Divisibility by 9 | | |
| 1.6.10 | Divisibility by 10 | | |
| 1.6.11 | Divisibility by 11 | | |
| 1.6.12 | Divisibility by 12 | | |
| 1.6.13 | Divisibility by 13 | | |
| 1.6.14 | Divisibility by 14 | | |
| 1.6.15 | Divisibility by 15 | | |
| 1.6.16 | Divisibility by 16 | | |
| 1.6.17 | Divisibility by 17 | | |
| 1.6.18 | Divisibility by 18 | | |
| 1.6.19 | Divisibility by 19 | | |
| 1.6.20 | Divisibility by 20 | | |
| 1.6.21 | Other Divisibility Rules. How Relatively Prime Numbers Determine the Divisibility Rules. | | |
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Enjoy the "Divisibility by 20" math lesson? People who liked the "Divisibility Rules lesson found the following resources useful:
- Divide By 20 Feedback. Helps other - Leave a rating for this divide by 20 (see below)
- Arithmetic Math tutorial: Divisibility Rules. Read the Divisibility Rules math tutorial and build your math knowledge of Arithmetic
- Arithmetic Video tutorial: Divisibility Rules. Watch or listen to the Divisibility Rules video tutorial, a useful way to help you revise when travelling to and from school/college
- Arithmetic Revision Notes: Divisibility Rules. Print the notes so you can revise the key points covered in the math tutorial for Divisibility Rules
- Arithmetic Practice Questions: Divisibility Rules. Test and improve your knowledge of Divisibility Rules with example questins and answers
- Check your calculations for Arithmetic questions with our excellent Arithmetic calculators which contain full equations and calculations clearly displayed line by line. See the Arithmetic Calculators by iCalculator™ below.
- Continuing learning arithmetic - read our next math tutorial: Decimal Number System and Other Numbering Systems
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