# Maths

Thursday

WALT: convert lengths

Today we are going to revise how we convert units of measurement for length.  What are units of measurement for length, though? Have a watch first of these BBC bitesize clips:

So how do we convert from one to the other? The answer is in multiplying and dividing by 10, 100 and 1000. We've worked hard on our place value so we should have a fairly good idea of how to do that.

We mentioned the multiplying and dividing by 10, 100 and 1000 in our zoom lesson last week however just to remind you if you cannot remember, you need to use your place value columns.

As you know, every place value column is 10 times bigger or smaller than the column next to it.  So the tens column is 10 times bigger than the ones column, the hundreds are 10 times bigger than the tens, and so on.  This means that when we multiply, we move our digits to the left.  If we multiply by 10, we move one column, 100 will be two columns and 1000 will be three columns.

For example:  if we look at the number 7.4, we would write it like this:

Th       H        T       O      .       t       hth

7       .       4

If we MULTIPLY by 10, we must move the digits 1 place to the LEFT.  This means moving the 7 from the ones column to the tens column and the 4 from the tenths column to the ones column resulting in an answer of 74.

Th       H        T       O      .       t       hth

7        4

If we multiply by 100, we must move the digits 2 place to the LEFT.  This means moving the 7 from the ones column to the hundreds column and the 4 from the tenths column to the tens column.  We must have a digit in the ones column, so we have to add a 0 in the ones column which is called a PLACE HOLDER.  This means the answer of 7.4 x 100 is 740.

Th       H        T       O      .       t       hth

7        4         0

When DIVIDING, the method is exactly the same, except the numbers move to the RIGHT.

There is a powerpoint in Resources should you wish to have a look.  Try one of the challenges in Resources, and concentrate on how you multiply or divide by 10, 100 and 1000.  Just below, you will a table explaining how you convert between millimetres, centimetres, metres and kilometres.  Look at the length you are starting with and work out what arrow you need to follow to get to the length you are converting to.

There is also a quite difficult, differentiated tarsia (puzzle) if you would like to challenge yourself.

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