20th Problem 2016

Use the Pythagorean theorem, where $a^2 + b^2 = c^2$ . Substitute the values we are given to get $153.6^2 + y^2 = 213.6^2$ . This becomes $23592.96 + y^2 = 45624.96$ . Subtract the values to get $y^2 = 22032$ . Square root both sides to get $y = 148.431802522$ . We have to round this to the tenth place so $y = 148.4$ .