Question

Marley bakes a rectangular cake that is 20 inches wide, 12 inches long and 6 inches high. She removes the cake from the pan to frost it. How many square inches of frosting does she need?

Answer 1

we know that
surface area of rectangular cake=area of the base+perimeter of base*height

only the top area is considered for frosting

area of the base=20*12----> 240 in²

perimeter of the base=2*[20+12]----> 64 in
height=6 in

surface area of rectangular cake=240+64*6----> 624 in²

the answer is
624 in²