Max has 5 red model cars. one third of his model cars are red.

Given:

5 red model cars

1/3 of his model cars are red.

This means that 5 is 1/3 of Max's collection. To get the number of his whole collection, we simply divide 5 by 1/3.

5 : 1/3 ⇒ 5 x 3/1 = 15

Max has a total of 15 cars in his collection.

Since 5 is 1/3 of the number of cars he has, 15 is the total number of cars