GMAT OFFICIAL GUIDE PS – √80 + √125 =
To solve the problem we must simplify the radicals. Radicals should be simplified whenever possible. Since the square root of a perfect square produces integers, it will often be helpful to locate and simplify perfect squares within a radical expression. Thus, we first locate the perfect squares that divide evenly into 80 and 125, making the simplification of each radical straightforward.
√80 = √16 x √5 = 4√5
√125 = √25 x √5 = 5√5
Now we can add these two results together. Remember to keep the value inside the radical constant and add together the values on the outside.
4√5 + 5√5 = 9√5