# e-book My Multiplication Book: Learn to Multiply – Numbers from 1-10

For example:. Where one number being multiplied is sufficiently small to be multiplied with ease by any single digit, the product can be calculated easily digit by digit from right to left. This is particularly easy for multiplication by 2 since the carry digit cannot be more than 1. Thus, the product is First multiply that number by 10, then divide it by 2. The two steps are interchangeable i. Add a zero to right side of the desired number. Next, starting from the leftmost numeral, divide by 2 B.

The resulting number is This is not the final answer, but a first approximation which will be adjusted in the following step:. Divide by 2. We can divide each digit individually to get Dividing smaller number is easier. Similarly, by adding instead of subtracting, the same methods can be used to multiply by 11 and 12, respectively although simpler methods to multiply by 11 exist. Hold hands in front of you, palms facing you. Assign the left thumb to be 1, the left index to be 2, and so on all the way to right thumb is ten.

The right little finger is down. Take the number of fingers still raised to the left of the bent finger and prepend it to the number of fingers to the right. Ex: There are five fingers left of the right little finger and four to the right of the right little finger. To multiply an integer by 10, simply add an extra 0 to the end of the number. To multiply a non-integer by 10, move the decimal point to the right one digit.

In general for base ten, to multiply by 10 n where n is an integer , move the decimal point n digits to the right. If n is negative, move the decimal n digits to the left.

### Lesson Outline

The product for any larger non-zero integer can be found by a series of additions to each of its digits from right to left, two at a time. First take the ones digit and copy that to the temporary result. Next, starting with the ones digit of the multiplier, add each digit to the digit to its left. Each sum is then added to the left of the result, in front of all others. If a number sums to 10 or higher take the tens digit, which will always be 1, and carry it over to the next addition. Finally copy the multipliers left-most highest valued digit to the front of the result, adding in the carried 1 if necessary, to get the final product.

In the case of a negative 11, multiplier, or both apply the sign to the final product as per normal multiplication of the two numbers. Another method is to simply multiply the number by 10, and add the original number to the result.

## Multiplying by Whole Tens and Hundreds

If you have a two-digit number, take it and add the two numbers together and put that sum in the middle, and you can get the answer. And the answer is To easily multiply 2 digit numbers together between 11 and 19 a simple algorithm is as follows where a is the ones digit of the first number and b is the ones digit of the second number :. Assign 6 to the little finger, 7 to the ring finger, 8 to the middle finger, 9 to the index finger, and 10 to the thumb. Touch the two desired numbers together. The point of contact and below is considered the "bottom" section and everything above the two fingers that are touching are part of the "top" section.

The answer is formed by adding ten times the total number of "bottom" fingers to the product of the number of left- and right-hand "top" fingers. In this example, there are 5 "bottom" fingers the left index, middle, ring, and little fingers, plus the right little finger , 1 left "top" finger the left thumb , and 4 right "top" fingers the right thumb, index finger, middle finger, and ring finger.

Five bottom fingers make 5 tens, or Two top left fingers and three top right fingers make the product 6. Summing these produces the answer, Here's how it works: each finger represents a number between 6 and When you join fingers representing x and y , there will be 10 - x "top" fingers and x - 5 "bottom" fingers on the left hand; the right hand will have 10 - y "top" fingers and y - 5 "bottom" fingers.

This technique allows easy multiplication of numbers close and below The product of two variables ranging from will result in a 4-digit number. The first step is to find the ones-digit and the tens digit.

## Multiplication Facts That Stick: How to Teach the Times Tables

Subtract both variables from which will result in 2 one-digit number. The product of the 2 one-digit numbers will be the last two digits of your final product. Next, subtract one of the two variables from Then subtract the difference from the other variable. That difference will be the first two digits of your final product. And the resulting 4 digit number will be the final product.

It may be useful to be aware that the difference between two successive square numbers is the sum of their respective square roots. Take a given number, and add and subtract a certain value to it that will make it easier to multiply. Add and subtract 8 the difference between and to get. Meaning the square of mn can be found by adding n to mn , multiplied by m , adding 0 to the end and finally adding the square of n. Suppose we need to square a number x near We know that 50 2 is So we subtract n from , and then add n 2. In other words, the square of a number is the square of its difference from fifty added to one hundred times the difference of the number and twenty five.

For example, to square 62, we have:. In other words, the square of a number is the square of its difference from one hundred added to the product of one hundred and the difference of one hundred and the product of two and the difference of one hundred and the number. For example, to square 93, we have:. An easy way to approximate the square root of a number is to use the following equation:.

The closer the known square is to the unknown, the more accurate the approximation. For instance, to estimate the square root of 15, we could start with the knowledge that the nearest perfect square is 16 4 2. So the estimated square root of 15 is 3. The actual square root of 15 is 3.

One thing to note is that, no matter what the original guess was, the estimated answer will always be larger than the actual answer due to the inequality of arithmetic and geometric means. Thus, one should try rounding the estimated answer down. Extracting roots of perfect powers is often practiced. The difficulty of the task does not depend on the number of digits of the perfect power but on the precision, i. In addition, it also depends on the order of the root; finding perfect roots, where the order of the root is coprime with 10 are somewhat easier since the digits are scrambled in consistent ways, as we shall see in the next section.

An easy task for the beginner is extracting cube roots from the cubes of 2 digit numbers. For example, given , determine what two digit number, when multiplied by itself once and then multiplied by the number again, yields Before learning the procedure, it is required that the performer memorize the cubes of the numbers Observe that there is a pattern in the rightmost digit: adding and subtracting with 1 or 3. Starting from zero:. There are two steps to extracting the cube root from the cube of a two digit number.

Say you are asked to extract the cube root of Begin by determining the one's place units of the two digit number. You know it must be one, since the cube ends in 1, as seen above. Note that every digit corresponds to itself except for 2, 3, 7 and 8, which are just subtracted from ten to obtain the corresponding digit.

## The Best Books to Teach Multiplication and Division

The second step is to determine the first digit of the two digit cube root by looking at the magnitude of the given cube. Here, 29 is greater than 1 cubed, greater than 2 cubed, greater than 3 cubed, but not greater than 4 cubed. The greatest cube it is greater than is 3, so the first digit of the two digit cube must be 3. This process can be extended to find cube roots that are 3 digits long, by using arithmetic modulo These types of tricks can be used in any root where the order of the root is coprime with 10; thus it fails to work in square root, since the power, 2, divides into To approximate a common log to at least one decimal point accuracy , a few log rules, and the memorization of a few logs is required.

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One must know:. The first step in approximating the common logarithm is to put the number given in scientific notation. For example, the number 45 in scientific notation is 4. Next, find the log of a, which is between 1 and Start by finding the log of 4, which is. Unless these facts can be recalled automatically, students will struggle when learning more advanced math skills, not to mention the problems they may have conducting day-to-day transactions such as buying goods at a store.

Click on the printable multiplication table or chart you want and select the Print option to send them to your printer. These resources can be used as memory aids, for reference, or for drill type practice.

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