Explanation:
a rectangular prism (like this brick) has the same basic structure as a cube (like a die) : it has 6 sides.
while a die has 6 equal sides, a rectangular prism has 3 pairs of equal sides :
top and bottom
left and right
front and back
all we have to do is calculate the areas of the 6 rectangles and add them up. that's it.
your remember, the area of a rectangle is
length × width
in our case we have
top and bottom : 2.5×11.5 × 2 = 28.75×2 = 57.5 in²
left and right : 2.5×5 × 2 = 12.5×2 = 25 in²
front and back : 11.5×5 × 2 = 57.5×2 = 115 in²
so, the total surface area of the whole block is
57.5 + 25 + 115 = 197.5 in²