This time the grid has 50 squares. 25 are shaded. shaded/grid size=25/50=1/2. As a ratio this is 1:2, as a fraction it is 1/2; as a decimal, we count how many digits there are in the denominator and then we write 1 followed by as many zeroes: so, there is one digit in the numerator, giving us 10, which we multiply by 1/2, to give us 5. That means the equivalent of 1/2 is 5/10 or 5 tenths. The first decimal place after the decimal point is the tenths position. 0.1 means 1 tenth. So 5 tenths is 5 times as big: 0.5. 1/2 is 0.5 as a decimal. As a per cent (which means out of 100), we multiply 1/2 by 100=50, so 1/2 is 50%.
Another way of converting 1/2 into a decimal is to divide 2 into 1 like this:
.....0 . 5
2 | 1 . 0 (treat this as 10 but leave the decimal points lined up)