The square root of 85 is 9.2195445. The closest number to 85 that has a square root that is a whole number is 81, whose square root is 9.
The square root of a number is a number that can be multiplied by itself to equal the original number. For example, the square root of 81 is 9 because 9 x 9 = 81. Square roots can also be expressed as a negative number because a negative times a negative equals a positive. The square root of 81 can be expressed as -9 because multiplying -9 by -9 equals 81. A number is a perfect square if its square root is a whole number. The numbers 4, 16, 25 and 36 are considered perfect squares.