Does your teen remember long division?

Posted on 06. Aug, 2010 by Joan Azarva in Articles

Try this experiment: Ask your teen to sit down with a pencil and paper and solve this problem:
560,479 divided by 34. What happens?

Long division is a skill that seems to atrophy by the time many students with learning disabilities enter high school. Reviewing the process, as well as learning the simple divisibility tricks below, can go a long way in taking the frustration out of long division. (See conclusion for why this is important.)

Numbers Divisible by 2

Numbers are divisible by 2 if the ones digit is evenly divisible by 2.

This means that even numbers are divisible by 2.

Numbers Divisible by 3

Numbers are divisible by 3 if the sum of all the individual digits is evenly divisible by 3.

For example, the sum of the digits for the number 3627 is 18, which is evenly divisible by 3. Therefore, the number 3627 is evenly divisible by 3.

Numbers Divisible by 4

Whole numbers are divisible by 4 if the number formed by the last two individual digits is evenly divisible by 4.

For example, the number formed by the last two digits of the number 3628 is 28, which is evenly divisible by 4.

Therefore, 3628 is evenly divisible by 4.

Numbers Divisible by 5

Numbers are evenly divisible by 5 if the last digit of the number is 0 or 5.

Numbers Divisible by 6

Numbers are evenly divisible by 6 if they are evenly divisible by both 2 AND 3 (see rules above).

Numbers Divisible by 7

To determine if a number is divisible by 7, take the last digit off the number, double it, and subtract the doubled number from the remaining number.

If the result is evenly divisible by 7 (e.g. 14, 21, 28, etc), then the number is divisible by seven. This may need to be repeated several times.

Example: Is 3101 evenly divisible by 7?

Take off the last digit of the number, which is 1.

Double the removed digit, so the 1 becomes 2.

Then, subtract 2 from 310.

The difference is 308.

Repeat the process by taking off the 8 so 308 becomes 30.

Then, double the 8 so it becomes 16.

Subtract 16 from 30.

The difference in 14, which is a multiple of 7.

BINGO – 3103 is divisible by 7!

Numbers Divisible by 8

Numbers are divisible by 8 if the number formed by the last three individual digits is evenly divisible by 8.

Example, Is 305,624 divisible by 8?

The last 3 numbers are 624, which is evenly divisible by 8, therefore 305,624 is evenly divisible by 8.

Numbers Divisible by 9

Numbers are divisible by 9 if the sum of all the individual digits is evenly divisible by 9.

Example, is 3627 divisible by 9?

The sum of the digits (3 + 6 + 2 + 7) is 18, which is evenly divisible by 9.

BINGO – 3627 is divisible by 9!

Numbers Divisible by 10

A number is divisible by 10 only if the last digit is

zero

.

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In our hight-tech age, when solving math problems is as easy as pressing the buttons on a calculator, many students haven’t had enough experience working with numbers on their own; thus, they never develop a feel for numbers or a “math sense”.

This becomes an issue as students cross the threshold from high school to college. Many colleges prohibit the use of calculators on their placement exams. A student accustomed to relying on a calculator since the primary grades often forgets the process of long division. In college, this deficit often results in having to take developmental math where they must re-learn all the basic skills by hand in just a 15-week semester – YIKES!

Have your teen review the 4 basic math operations without a calculator, and make sure he/she knows his/her basic math facts cold. This will maximize the chances of placing into a higher math section in college.

Tags: divisibility tricks, math