The principal square root of 160 is 12.65 to two decimal places. The other square root of 160 is minus 12.65 to two decimal places. All real numbers have two square roots, one of which is the negative of the other.
A square root, x, of a number, n, is the value of x that satisfies the equation x^2 = n, where x^2 means x multiplied by x. The positive square root is called the principal square root. Most calculators will give only the principal square root when asked to calculate the square root of a positive real number, such as 160.