Constant of proportionality is the constant value of the two proportional quantities, in this problem p and s, where 4 is the factor of proportionality because it is constant or k.
In simple terms, p is in direct proportion to s wherein the increase or decrease in value of s results to the increase or decrease in value of p with 4 the only factor remaining unchanged.
In the above problem, the number 4 is derived from the word square. We all know that a square has 4 sides of equal lengths, therefore, the perimeter is equivalent to the product of 4 and its lenght.
The formula for a trapezoid is a= 1/2*(b1+b2)*h. B1 and b2 would represent the two bases given and therefore doesn't matter what order you put them in. Plug in all values into the equation and you'll get 1/2*(5+8)*5 then 1/2*(13)*5. Next simplify to get 6.5*5 which then equates to 32.5.