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Lesson 25: Patterns Involving Multiplication
Many test questions ask you to find the missing number in a pattern that involves multiplication, or in some cases, to continue the pattern. This lesson shows how.
Don't forget to watch the embedded video clip for this lesson at the bottom of the page. Please read the embedded video disclaimer if you have not already done so.
Take a look at this pattern: 1, 2, 4, 8, .... What number comes next? First we should check to see if the pattern involves addition. To get from 1 to 2, we add 1. To get from 2 to 4, we add 2. To get from 4 to 8, we add 4. This means the pattern doesn't involve addition, since we're not adding the same number each time.
Let's see if it involves multiplication. To get from 1 to 2, we can multiply by 2. To get from 2 to 4, we also multiply by 2. To get from 4 to 8, we again multiply by 2. This seems to be a pattern formed by multiplying each number by 2. To find the next number, we'll multiply 8 by 2 to get 16, which is the answer.
Take a look at this pattern: 1, 3, 9, ___, 81. What is the missing number? Just like above, we can see that this problem does not involve an adding pattern. In fact, you can see that it grows quite quickly to 81, so that's another clue that it can't involve addition. To get from 1 to 3, we multiply by 3. To get from 3 to 9, we also multiply by 3. Let's multiply 9 times 3 to get the missing number, and then check to see if it works in the pattern. 9 times 3 is 27, and 27 times 3 is 81. So the missing number is 27.
Remember, when you see a pattern question, first determine the operation being used, such as addition or multiplication, and then determine what amount is being added or multiplied.
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