The formula to calculate the surface area of a cube is given by

where
b is the long side of the cube
step 1
Find out the surface area of the cube with a side length of 15 inches

step 2
Find out the surface area of all 27 blocks
Remember that
27=3^3
so
The side length of the blocks is 15/3=5 in
Find out the surface area
![\begin{gathered} SA=27[6(5)^2] \\ SA=4,050\text{ in}^3 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/m2yrsk31fp8anfsnd8as587a9u94z4ix4j.png)
Compare both surface areas
4,050/1,350=3
therefore
The total surface area of the 27 blocks is 4,050 square inches. This is 3 times the surface area of the box