Students and teachers of two graduating classes in Grade Three *** 150 took photos of graduation photo on the steps, and the photographer arranged them in a trapezoidal queue with more in front and le

Students and teachers of two graduating classes in Grade Three *** 150 took photos of graduation photo on the steps, and the photographer arranged them in a trapezoidal queue with more in front and less in back. Suppose there are k people in the front row and there are n rows in * *, then the number of people from front to back in each row is k, k+ 1, k+2, k+(n- 1), which means kn+n(n? 1) 2 = 100, that is, n[2k+(n- 1)]=200, because both k and n are positive integers, and n≥3, so n < 2k+(n- 1), and n and 2k+. When n=8, k = 9. Therefore, * * * has two different schemes.