There are 35 students going to the zoo. Each van can hold 6 students. How many vans are needed?

You will need 6 vans, as 5 vans will seat 30, but you still have 5, so you'll need one additional that'll just have an empty seat.

You will need 6 buses for all 35 students. The reason you need six buses instead of five because 6 x 6 = 36 and if you only get 5 buses for the 35 students, then there are gonna be 5 students that aren't going to the zoo. 6 x 6 = 36. 6 x 5 = 30