1. Are there any numbers that cannot be written as a decimal?

Yes there are. You may have used (pi) when finding the area of a circle. This number cannot be written EXACTLY as a decimal. It can be approximated as the fraction 22/7

2. Computers use numbers to a base of 2, what base do decimals work to?

Decimals are expressed to base 10 .

3. When MULTIPLYING a decimal number by 1000 in which direction does the decimal point move?

To the RIGHT (by 3 places.) i.e. The number becomes 1000 time greater.

4. How do you divide by a number with a decimal point in it?

The easiest way is to multiply the number by 10, 100 or 1000 etc until the number DOES NOT have a point in it!
You must then do the same to the number you are dividing into. i.e. 34.5 ÷ 3.6 = 345 ÷ 36
This is now much easier to work out!