# Maths

Time to practice our place value knowledge, which is crucial for a good understanding in maths. We'll be multiplying and dividing by 10 and 100. Here's how to do it!

Let's say we have the number 5.7 - 5 units and 7 tenths. Watch what happens to each digit when I click 'x 10' Each digit has moved one place value to the left - those 7 tenths are now 7 units (because we've 10 times as many) and those 5 units are now 5 tens (again, we've got ten of them!). Moving the digits in a place value grid is probably the easiest way to understand this one.

Watch what happens if we divide a number by 10. I'll pick for our example 36.1. I've put the grid lines on for this one to make it easier to understand; When I click ÷ 10, each digit moves one place to the right - we've made every single one of the digits 10 times smaller. If we made 30 ten times smaller we'd only have 3 - so that 3 moves from the tens to the units. All the digits move at the same time - the 3 moves to the right, the 6 stays right next to it, the 1 stays right next to the 6. Don't make the mistake of leaving gaps, or swapping or changing the digits. They just move, that's it!

But Mr Davies, what about multiplying or dividing by 100? Well, with multiplying or dividing by 10, we moved the digit 1 place value. For 100, you move it 2! Another way of thinking of it is if you have to divide by 100, divide it by 10, twice!

For 1000, you'd move it 3! For 10,000...well, you get the idea.

Below are some questions to try in your book. Use a place value grid like the one above if you need to. The questions in the red area are challenge questions if you're a brainbox and blast through the ones on the top - good luck!

Top