Start from zero — the basic math you need before everything else
A square root undoes squaring. Squaring 5 gives 5² = 25, so the square root of 25 (written √25) is 5. The √ symbol asks: "what number, multiplied by itself, gives this?"
Numbers whose roots come out as whole numbers are called perfect squares: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100. Most numbers aren't perfect squares, but you can still estimate their roots by finding the two perfect squares they fall between.
A square root is a side length. A square rug covering 25 square feet has sides of √25 = 5 feet, because 5 × 5 = 25. If you know the area of a square room, the square root tells you how long one wall is.
▶ Square Roots