The square root of 189 is equal to 3 times the square root of 21, or approximately 13.75. To simplify the square root of a number, the number must first be broken down into its factors, looking especially for perfect squares.
In this case, 189 is equal to 9 — a perfect square — times 21. The square root of each factor is then taken separately. The square root of 9 is 3, and the square root of 21 cannot be simplified further and is commonly left under the radical, which is another term used to refer to the square root sign.