Podcast
Questions and Answers
If a number is divisible by 11, what is also true?
If a number is divisible by 11, what is also true?
- The sum of its digits is 11
- The original number is divisible by 11 (correct)
- The number is odd
- The number is even
In the example using 121, what is the sum of the digits in the odd places?
In the example using 121, what is the sum of the digits in the odd places?
- 3
- 1
- 0
- 2 (correct)
For a number to be divisible by 3, what must be true of the sum of its digits?
For a number to be divisible by 3, what must be true of the sum of its digits?
- The sum must be divisible by 3 (correct)
- The sum must equal 3
- The sum must be odd
- The sum must be even
In the number 8550*1, what value of * makes the number divisible by 3?
In the number 8550*1, what value of * makes the number divisible by 3?
What is the first step in checking if 121 is divisible by 11, as done in the example?
What is the first step in checking if 121 is divisible by 11, as done in the example?
What is calculated after summing the digits in the even and odd places when testing divisibility by 11?
What is calculated after summing the digits in the even and odd places when testing divisibility by 11?
If the difference between the sum of odd and even placed digits is 0, what does this mean for divisibility by 11?
If the difference between the sum of odd and even placed digits is 0, what does this mean for divisibility by 11?
What is the purpose of finding the 'least value' in the example problems?
What is the purpose of finding the 'least value' in the example problems?
In math problems like the ones shown, what does the asterisk (*) typically represent?
In math problems like the ones shown, what does the asterisk (*) typically represent?
Flashcards
Divisibility rule for 11
Divisibility rule for 11
If subtracting the smaller number from the larger number results in 0 or a number divisible by 11, then the original number is also divisible by 11.
Finding the missing digit for divisibility by 3
Finding the missing digit for divisibility by 3
To find the least value that makes 8550*1 divisible by 3, sum all the given digits (8+5+5+0+1=19) and find the next multiple of 3. The value required 2 to reach 21 which is a multiple of 3.
Finding the missing digit for divisibility by 11
Finding the missing digit for divisibility by 11
To find the least value that makes 13*1 divisible by 11, apply the divisibility rule for 11 by subtracting the number obtained from the bigger number obtained.
Study Notes
- Subtract the smaller number from the larger number obtained.
- If the resulting number is 0 or divisible by 11, then the original number is also divisible by 11.
- Example: 121 is divisible by 11 because the sum of the digits in the even place is 2, and the sum of digits in the odd places is 1+1=2, so 2-2=0, which is divisible by 11.
Solved Examples
- Problem: Find the least value of * for which the number 8550*1 is divisible by 3.
- Solution: Let the required number be a.
- 8+5+5+0+a+1 = 19+a
- The least number that satisfies the condition is 2.
- Problem: Find the least value of * for which the number 13*1 is divisible by 11.
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