Explanation:
1.
Given that,
L = 18 in , w = 20 in , h = 16 in
The surface area of the box is given by :
SA= 2lw + 2lh + 2wh
Put all the values,
SA= 2lw + 2lh + 2wh
= 2(lw+lh+wh)
= 2(18(20)+18(16)+20(16))
= 2 (968)
= 1936 in²
2.
L= 10.5 in , W= 15.5 in , H= 20 in
The surface area of the box is given by :
SA= 2lw + 2lh + 2wh
Put all the values,
SA= 2lw + 2lh + 2wh
= 2(lw+lh+wh)
= 2(10.5(15.5)+10.5(20)+15.5(20))
= 2 (682.75)
= 1365.5 in²
Hence, this is the required solution.