Doubling each time
for 3rd grade

Number patterns: double the number each time

This topic focuses on a number pattern where the next number is worked out by doubling the current one (multiply it by 2). This doubling pattern is easiest to understand by looking at examples. Let's start by looking at the simplest example:

1 , 2 , 4 , 8 , _ , _ ...

What comes next? To find out, let's first make sure this pattern is a doubling pattern by looking at the differences between each pair of numbers. You may notice that we are using multiply and divide because this pattern is a geometric sequence, not an arithmetic sequence.

• 2 ÷ 1 = 2
• 4 ÷ 2 = 2
• 8 ÷ 4 = 2

You can see that in each step, we multiply the previous number by 2 to get the next number in the sequence. That is because doubling a number is the same as multiplying it by 2. Now, let's use this rule to find the next number:

8 x 2 = 16

The next number in the pattern is 16. The sequence now looks like this:

1 , 2 , 4 , 8 , 16 , _ ...

If we do the next number in the sequence, it will be 16 x 2 which is 32,

1 , 2 , 4 , 8 , 16 , 32 ...

To recap, always remember the following steps when identifying the next number in a pattern that doubles the size of the number each time:

1. Confirm that the ratio between each pair of consecutive numbers is 2 by dividing them.
2. Multiply the last number in the sequence by this ratio of 2.
3. That gives you the next number in the sequence.

This topic asks you to work out the missing number in the pattern of numbers created by doubling the current number each time.

Related topics

• Add a number each time
• Subtract a number each time