300/55=5(辆)。。。25(人)租5辆大巴车和1 辆中巴车。5*500+1*400=2900(元)方案二:租4辆大巴车和2辆中巴。4*500+2*400=2800(元)方案三:租3辆大巴车和3辆中巴3*500+3*400=2700(元)答:租3辆大巴车和3辆中巴最省钱。(正好坐满。没有空位)
设租大巴车x辆,中巴车y辆,租金为z元55x+45y>=300z=500x+400y解得x=3,y=3,z最小,z=2700