- Created by: james jackson
- Created on: 31-05-11 20:19
Any number above zero is a positive number. Positive numbers are written with no sign or a '+' sign in front of them and they are counted from zero to the right.
Any number below zero is a negative number. Negative numbers are always written with a '-' sign in front of them and they are counted from zero to the left.
Always look at the sign in front of a number to see if it is positive or negative.
Positive numbers get higher the further we move right, so 5 is more than 2.
Negative numbers get lower the further we move left, so -5 is less than -2.
If you get 7 out of 10 in a test, you can write your score as 7/10.
7 expressed as a fraction of 10 is 7/10.
Similarly, if there are 20 socks in a drawer and 4 of them are blue, 4/20 of the socks are blue.
So, 4 expressed as a fraction of 20 is 4/20. We can put this into its simplest form by dividing the top and bottom numbers by 4. So we get 1/5.
If you are expressing a number as a fraction of a second, the first number goes on the top and the second number on the bottom.
We use a decimal point to separate units from parts of a whole (like tenths, hundredths, thousandths, etc).
- 0.1 is a tenth, 1/10 of a unit
- 0.01 is a hundredth, 1/100 of a unit
- 0.001 is a thousandth. 1/1000 of a unit
To multiply 237 by 4 without using a calculator, you can set it out like this:
Start with 4 × 7, which is 28, so write the 8 and carry the 2 to the tens column.
4 × 3 = 12, but remember to add the carried 2 to get 14. Write the 4 and carry the 1 to the hundreds column.
4 × 2 = 8, and we add the carried 1 to get 9.
Therefore 237 × 4 = 948
This method is called short multiplication.