The formula for this is m = 4a + 2c, where c = number of children; m = number of meatballs; a = number of adults.
m = (4 x 10) + (2 x 5)
simplify,
40 + 10 = 40
The answer to this is 40 meatballs.
The scale factor can change how big or small a figure is, though it will still be similar. For example, a triangle with two sides measuring 3 & 3 (isosceles) are scaled in a factor of 6 (becoming larger).
3 x 6 = 18
The new triangle will have the sides measuring 18. Even though the triangles are not congruent, they are similar.
hope this helps