5th box -Flashcards

The resulting equation is inversely proportional (not proportional, like a baking recipe). So, set up a proportional equation and then flip one of the sides. It is important to use the same units on each side! 15/9 = 21/x -> 15/9 = x/21 -> x=35.

On these types of problems, the units digit repeats every few powers. Write out them until it repeats, then extrapolate by counting from a multiple of the repeat interval.

1) Opposite sides and opposite angles are equal.

n!/(r!*(n-r)!)