If p,q, and r are three non-zero integers such that p+q+r=26 andp1+q1+r1+pqr360=1, compute pqr.
Solution — click to reveal
p1+q1+r1+pqr360pq+pr+qr+360360385=1=pqr=pqr−pq−pr−qr=(p−1)(q−1)(r−1)−(p+q+r)+1=(p−1)(q−1)(r−1)−25=(p−1)(q−1)(r−1) From here, you can factor 385 as 5⋅7⋅11, giving corresponding values of 6,8, and 12. The answer is 6⋅8⋅12=576.