Question

The surface area of a cuboid is 1372sq.cm. if its dimensions are in the ratio of 4:2:1, then length is

Answer 1

let lenght be:
4x,2x and x

then,
surface area of cuboid = 2(lb+bh+lh)
⇒1372= 2(4x*2x+2x*x+4x*x)
⇒1372= 2(8x²+2x²+4x²)
⇒1372= 2*14x²
⇒1372= 28x²
⇒1372/28 = x²
⇒49=x²
⇒√49=x
⇒7=x
or x=7

hence,​length of cuboid is 4 x 7 =28cm