There are a total of 115 first graders, 225 second graders, and 140 third graders, who are going on a field trip. If a bus holds 80 students, how many buses are necessary to transport all of the students? Total number of students: 115 + 225 + 140 = 480 Number of buses needed: 480 + 80 = b Total number of students: 115 + 225 + 140 = 480 Number of buses needed: 480 − 80 = b Total number of students: 115 + 225 + 140 = 480 Number of buses needed: 480 × 80 = b Total number of students: 115 + 225 + 140 = 480 Number of buses needed: 480 ÷ 80 = b