Can somebody please help me find the surface area of this shape

Hi!

There are three different rectangles that make up this closed box. We need to calculate the area of them to find the surface area of this shape. Here are the measurements:

Rectangle 1: 40 * 20

Rectangle 2: 50 * 20

Rectangle 3: 50 * 40

Note that there are two of each type of rectangle, so when we are done calculating the area of each rectangle we will multiply each by 2.

Rectangle 1: 40 * 20 = 800(2) = 1600

Rectangle 2: 50 * 20 = 1000(2) = 2000

Rectangle 3: 50 * 40 = 2000(2) - 4000

Now, we add the areas together: 1600 + 2000 + 4000 = 7600

The surface area of this closed box is 7600cm squared.

Hope this helps!

hello from mrbilldoesmath!

answer:

25x^2 + 90x + 84

discussion:

mn(x) = m(n(x)) = m( 5x + 9) =

(5x + 9)^2 + 3 =>

25x^2 + 90x + 9^2 + 3 =

25x^2 + 90x + 84                 (as 9^2 = 9*9 = 81)

which is the second choice

regards,  

mrb

p.s.   i'll be on vacation from friday, dec 22 to jan 2, 2019. have a great new year!