How to Add and Subtract on the Number Line
How to Solve Problems with a Cartesian Graph
How to Divide Numbers on the Number Line

How to Multiply Large Numbers

The main reason to know the multiplication table is so you can more easily multiply larger numbers. For example, suppose you want to multiply 53 x 7. Start by stacking these numbers on top of another, aligning the ones place. Draw a line underneath, and then multiply 3 by 7. Because 3 x 7 = 21, write down the ones digit (1) and carry the tens digit (2) to the tens column:

image0.jpg

Next, multiply 5 by 7. This time, 5 x 7 = 35. But you also need to add the 2 that you carried over, which makes the result 37. Because 5 and 7 are the last numbers to multiply, you don't have to carry, so write down the 37 — you find that 53 x 7 = 371:

image1.jpg

When multiplying larger numbers, the idea is similar. For example, suppose you want to multiply 53 by 47. Be sure to align the stacked numbers by the ones place. (The first few steps — multiplying by the 7 in 47 — are the same, so pick up the next step.) Now you're ready to multiply by the 4 in 47. But remember that this 4 is in the tens column, so it really means 40. So to begin, put a 0 directly under the 1 in 371:

image2.jpg

This 0 acts as a placeholder so that this row is aligned properly.

When multiplying by larger numbers with two digits or more, use one placeholding zero when multiplying by the tens digit, two placeholding zeros when multiplying by the hundreds digit, three zeros when multiplying by the thousands digit, and so forth.

Now you multiply 3 x 4 to get 12, so write down the 2 and carry the 1:

image3.jpg

Continuing, multiply 5 x 4 to get 20, and then add the 1 that you carried over, giving a result of 21:

image4.jpg

To finish, add the two products (the multiplication results):

image5.jpg

So 53 x 47 = 2,491.

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How to Work with Inequalities
How to Evaluate Expressions with Powers
The Basics of Pie Charts
How to Round Numbers Up and Down
How to Use the Distributive Property of Multiplication
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