Let the length of the diameter be d and radius be r, thus to solve for d we proceed as follows: r²+31²=(r+15)² solving for d we solve for r r²+961=r²+30r+225 putting like terms together we obtain: r²-r²+961-225=30r 736=30r solving for r r=24.53 thus d=24.5333×2 d=49.067~49.1 Answer is D. 49.1
