I have difficulty reading the numbers.
I'll explain the surface area of the first one.
Code:* * * * * 20 * * * * * * * * 12 * * * * * * * * * 14 * * * * * * * * * 16
The front face is a right triangle with base 16 and height 12.
. . Its area is: .
The rear face is identical.
The left face is a rectangle.
The sloping right face is a rectangle.
The bottom face is a rectangle.
Total surface area: .
4) Volume: 288 = Correct, Surface area: 368 = Incorrect.
Divide the shape into 3 parts - 2 triangular prisms and 1 rectangular prism.
Just calculate the surface area of each face and then add them together.
6) (I'm guessing the depth of this one is 10, it is almost cut off)
Volume: 2520 = Correct, Surface area: 1684 = Incorrect. (Hint: It is under 1500)
To me it seems that all of your volume calculations are correct, but your surface area is over what it actually is. How are you working out your surface area? Show ALL of your working so we can tell what you did wrong.