Question 205878
if you find the square grid size, you can find the number of characters


let x="first grid edge", so x+1="second grid edge"


"a square grid with equal number of rows and columns, found that 24 characters were left out."
___ x^2 + 24


"add one more row and column, he found that he was short of 25 characters"
___ (x + 1)^2 - 25


the two expressions are equal to the number of characters; and, therefore, to each other


x^2 + 24 = x^2 + 2x + 1 - 25


48 = 2x ___ 24 = x


substituting to find the number of characters ___ 24^2 + 24 = 600