Count forwards and backwards in powers of 10 | Year 5 Maths

## 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.

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## Example Questions

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.

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.

## Times Table Flash Cards

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