The number of tickets to sell at the door is 48 tickets.
Step-by-step explanation:
Let 'x' be the number of tickets need to sell at the door.
5x + 4(40) = 400
5x + 160 = 400
5x = 240
x = 240/5
x = 48 tickets
The number of tickets to sell at the door is 48 tickets.