PSAT10 P1 · 第 18 题

Quadrilateral P'Q'R'S' is similar to quadrilateral PQRS, where P, Q, R, and S correspond to P', Q', R', and S', respectively. The measure of angle P is 30°, the measure of angle Q is 50°, and the measure of angle R is 70°. The length of each side of P'Q'R'S'  is 3 times the length of each corresponding side of PQRS. What is the measure of angle P '?