A number line is infinite in both directions. Decimals, like fractions, are a way of describing points on the number line that fall in between the whole numbers. If you were using fractions, you'd [...]
A fraction of a pie If you want to add two fractions together, both fractions must have the same denominator. That's okay if you want to add 1/9 and 4/9 = 5/9. But what if [...]
An infinite distance: stars in the sky Why do we use exponents? Some numbers are so big that it's hard to write them in the regular way. The number line [...]
Calculating the area of your room. The area of a room is the size of the floor. Suppose you wanted to find out whether your room was really bigger than [...]
This is an equilateral triangle. A triangle is any set of three points on a plane and the lines connecting those points to each other, as long as the three points aren't all on the [...]
This is a trapezoid. A trapezoid is a kind of quadrilateral that has at least two sides that are parallel to each other. A parallelogram is a trapezoid that has two pairs of parallel [...]
This is a square. The darker purple line is the perimeter of the square. A square is a flat shape, in one plane, defined by four points at the four corners. A square [...]
This is a sphere. A sphere is a three-dimensional circle. Or you could say that a sphere is the set of all the points that are at the same distance from the center [...]
Pyramid Just as a plane is made of an infinite number of lines, a solid is made of an infinite number of planes. These planes are right next to each other, like [...]
These two green lines are skew to each other. Skew is a pretty cool word, and it sounds like it means something really weird, and it kind of does. It [...]
