The 6 Rules When you multiply powers of the same number you add the powers. When you divide powers of the same number you subtract the powers. When you put a power outside a bracket you multiply the powers. Negative powers mean reciprocal or 'one over.....' When the power is a fraction the top of the fraction is a power and the bottom of the fraction is a root. Anything to the power of zero is simply equal to 1. Standard Form Any number can be written in the form a x 10n where a is a number between 1 and 10 and b is an integer. Indices in Algebra Algebraic fractions can be simplified by following Rule 2 of Indices and taking the powers on the bottom away from the powers on the top or, in other words, cancelling the powers.