25% means the same as  which reduces to 

All three mean the same thing.

1. Twenty-five percent of a piece of pie.
2. Twenty-five one hundredths of a piece of pie.
3. One fourth of a piece of pie.

All those mean exactly the same thing.

The easy way to divide by 100 is to move the decimal two places to the left.

25% means 25.% [The decimal is invisible). Move the invisible decimal two
places left and make it visible, take away the % symbol and you have  .25,
which is the same thing as 25% and also the same thing as 
which is also the same thing as .

Edwin