1: Suppose: the time to walk past the rostrum is t275. Students form 55 rows with a spacing of1m. If the queue length is 54M, then 40t=34+55- 1 and t = 2.2 > 2 will not pass, because X: Y: Z = 3: 4: 2. Z=7k Because 2x-3y+z =18k+7k = 18, so k =18, so x=54, y=72, z= 126, so x+y+z =.