**Count forwards and backwards in powers of 10** *KS2 Revision*

## What you need to know

**Things to remember:**

- When counting forwards or backwards in 10s, 100s, 1000s, or 10000, this is the same as adding or subtracting this amount.

We get powers of 10 by starting with 1 and multiply by 10.

1\times10=10

10\times10=100

100\times10=1000

1000\times10=10000

So, our powers of 10 are: 1, 10, 100, 1000, 10000…

Let’s start by adding 10s to 2135

2135

2135+10=2145

2145+10=2155

2155+10=2165

And we can create a sequence; 2135, 2145, 2155, 2165…

Looking at the sequence we can see that the next number will be 2175.

*What is the next number in the sequence?*

**3400, 3500, 3600, 3700, …**

First, we have to see how much our sequence is changing by. If we choose two numbers next to each other, we can see that we’re adding 100 each time.

3400

3400+100=3500

3500+100=3600

3600+100=3700

To find the next number in the sequence, we have to add 100 to the last number.

3700+100=3800

The next number in the sequence is 3800.

*What is the next number in the sequence?*

*9780, 8780, 7780, 6780, …*

First, we have to see how much our sequence is changing by. If we choose two numbers next to each other, we can see that we’re subtracting 1000 each time.

9780

9780-1000=8780

8780-1000=7780

7780-1000=6780

To find the next number we have to subtract 1000 from the last number.

6780-1000=5780

So, the next number in the sequence will be 5780.

## Example Questions

**Question 1: ***What is the next number in t**he sequence?*

*7430, 7420, 7410, 7400, … *

First, we have to see how much our sequence is changing by. If we choose two numbers next to each other, we can see that we’re subtracting 10 each time.

7430

7430 +10=7420

7420+10=7410

7410+10=7400

To find the next number we have to subtract 10 from the last number.

7400-10=7390

So, the next number in the sequence will be 7390.

**Question 2: ***What is the next number in the sequence?*

*2500, 3500, 4500, 5500, … *

First, we have to see how much our sequence is changing by. If we choose two numbers next to each other, we can see that we’re adding 1000 each time.

2500

2500 +1000=3500

3500+1000=4500

4500 +1000=5500

To find the next number we have to add 1000 to the last number.

5500-1000=6500

So, the next number in the sequence will be 6500.