Because odd number plus even number equals odd number, the number of cars satisfying these two types is odd.

Also, because a bicycle has two wheels (even number) and a tricycle has three wheels (odd number), the number of wheels is odd. Any multiple of even number is even number, and odd multiples of odd number are odd number.

This question has been tested: the sum of odd and even numbers is odd, and the product of odd and even numbers is odd.