Question 112379
First, you can write the equation for the amount of topping needed per layer of cake. The number of cake layers is 7 and each layer is 9 inches in diameter, which means the radius is half of that or 4.5 inches.
So the area of one layer is: {{{A = (pi)(4.5)^2}}} or {{{A = (3.14)(20.25)}}}={{{63.585}}}sq. in.
Let the number of batches of topping be B and each topping will cover 65 sq. in. of cake.
So you can write:
{{{B = 7(63.585)/65}}}
{{{B = 445.095/65}}}
{{{B = 6.847}}} Round up to the nearest integer.
{{{B = 7}}}batches.