Do You Know Your Divisibilities? Quiz

Answer: No

When checking to see if a number is divisible by 2 you check the last digit. The way to look at it is 2 to the first power makes it require the last digit.

Answer: 1

Because 4 is 2 squared, the last 2 digits of the number have to be divisible by 4 for the whole thing to be divisible by 4.

Answer: 3

8 = 2 to the 3rd power; therefore, the last 3 digits have to be divisible by 8 for the entire number to be divisible by 8. If you want to know if a number is divisible by a 2 to the power of p, just test the last p digits.

Answer: Yes

Any number that ends in 5 or 0 is divisible by 5.

Answer: 0,3,6 or 9

To tell if a number is divisible by 3, you need to sum the digits, and if the sum of the digits are divisible by 3 than the entire number is divisible by 3.

Answer: 2

When testing to see if a number is divisible by nine, you use the same technique as for three only the sum of the digits has to be divisible by 9.

Answer: false

This method works for a divider of eleven, not thirteen. Also it works if the results equal 0. 44 equals 11 * 4 so it is divisible by 11 but 4-4 = 0, so the rule has to include 0. 52789 = 4799*11 the 5+7+9 = 21 2+8 = 10 21-10 = 11 therefore it has to be divisible by 11 by this rule. I haven't heard of a rule for 13 yet.

Answer: Yes

The method I know is taking every other three digits and summing them and subtracting from the remaining digits and if that's divisible by 7 it's divisible by 7. The problem is it only works for a minimum of 4 digit number, and it's easier to just do the division. One example is 1701 is divisible by 7 because 701-1= 700 and 700 is divisible by 7 so the number is divisible by 7.

Answer: p=6 and q=0

For the number to be even and divisible by 5 q has to be 0. The last three digits have to be divisible by 8 for the entire number to be. One step at a time makes this problem easy.

Answer: 3

To start this problem you need to find out what q could be using the 8 rule (getting 3 or 7) and then p using the 11 rule (which gives 3 if q=3 but 10 - an impossible value - if q=7).

By the way, If both 9 and 3 are dividers in a multiple choice question with only one correct answer, 9 is automatically ruled out. 9 is 3 squared so anything divisible by 9 is also divisible by 3. This question was similar to a question I had in college when I was practicing for a math contest.