bbc.co.uk
Home
Explore the BBC
  Key Ideas
 
  Builder Ted

Place value
Place value is the basis of our number system. The position of a digit gives it its value.

The digits further to the left have larger values than those to the right.

E.g. 234

The 2 is in the 'hundreds' column, and has the value of 200.
The 3 is in the 'tens' column, and has the value of 30.
The 4 is in the 'units' column, and has the value of 4.

Decimals
Decimals are a continuation of the number system, and the decimal point marks the change from whole numbers to fractions.

E.g. 6.49

6 is in the 'units' column, and has a value of 6.
4 is in the 'tenths' column, and has a value of 4/10.
9 is in the 'hundredths' column, and has a value of 9/100.

Placing numbers in order of size
When comparing the size of two numbers, we always look at the digits furthest to the left.

E.g. Which is bigger, 135 or 137?

hundreds tens units
1 3 5
1 3 7

The numbers in the 'hundreds' and 'tens' columns are the same, but when we compare the 'units' column, we see that 7 is bigger than 5. Therefore, 137 is bigger than 135.

E.g. Which is bigger, 4.2 or 4.07?

units   tenths  hundredths
4 . 2  
4 . 0 7

The numbers in the 'units' columns are the same, but when we compare the 'tenths' column, we see that 2 is bigger than 0. Therefore, 4.2 is bigger than 4.07.

Negative Numbers
Positive numbers are greater than 0.
Negative numbers are less than 0.

-6   -5   -4   -3   -2  -1   0   1   2   3   4   5   6

We always count away from 0, so 6 is greater than 4, but -6 is less than -4.

E.g. Place the numbers 5, -7, -2, -5, 1 in order of size, smallest first.

-7, -5, -2, 1, 5

Back to top
close