The sum of the dimensions of a cuboid is 21 cm . if its diagonal is 7√5 cm find its surface area.

Question

PLEASE MENTION THE STEPS BELOW

Answer 1

l+w+h=21

square both sides

l^2+w^2+h^2+2lw+2lh+2wh=441

the diagonal of the cuboid is √(l^2+w^2+h^2)

√(l^2+w^2+h^2)=7√5

square both sides

l^2+w^2+h^2=245

substitute

245+2lw+2lh+2wh=441

2lw+2lh+2wh=441-245

total surface area=196 sq cm