Ineed the surface area for this composite figure, i already cut it in 3 shapes, but i don't know what to do next. !

Hello!

You find the area of all three shapes and add them together

We can do the one on the left first

To find the area we multiply the sides

8 * 7 = 56

The one on the left has an area of 56 ft squared

Now lets do the one on the right

8 * 7 = 56

The one on the left has an area of 56 ft squared as well

Finally lets do the one in the middle

We first have to find the length

8 + 12 = 20

Now we multiply

20 * 20 = 400

The middle one has an area of 400ft squared

Now we add them together

56 + 56 + 400 = 512

The answer is 512ft squared

Hope this helps!

The diagonal forms a right isosceles triangle whose hypotenuse is x√2 where x is the length of a side of the square face
so, x√2=5
x=5/√2
x=5/1.414
x=3.536 cm
you can also use the Pythagorean Theorem to get the length of a side, x
5^2=x^2+x^2
25=2x^2
x^2=25/2
x^2=12.5
x=√12.5
x=3.535 cm
the volume is V=3.536^3
V=3.536*3.536*3.536
V=44.2 cm^3
my answer has more accuracy, therefore you choose D) which is closest to my answer