Question

What will be the lateral surface area (inch ${}^2$) of the cube formed by folding up this cardboard cross ?

Answer 1

The cardboard cross has $6$ squares and the side of all the squares is $7.5"$.
When folded, it will form a cube with $s=7.5"$, like this:



Thus, lateral surface area of the cube $=4\times s^2$
$=4\times 7.5\times 7.5$
$=4\times 56.25$
$=225$ inch${}^2$