Question

The dimensions of a cuboid are in the ratio of 1:2:3 and its total surface area is 88 cm2, then
its lateral surface area is :
(A) 70 cm2
(B) 72 cm2
(C) 74 cm²
(D) 76 cm2​

Answer 1

let dimensions of cuboid is x.

1x,2x,3x

total surface area of cuboid is 2(lb+bh+lh)

L= 1x, B= 2x, H=3x

88=2(1x*2x+2x*3x+1x+3x)

88= 2(2x²+6x²+3x²)

88= 2(11x²)

88=22x²

x²=88/22

x²= √4

x=2

1x=1*2=2cm

2x=2*2=4cm

3x=3*2=6cm

now, dimensions of cuboid is 2cm,4cm,6cm

lateral surface area of cuboid is 2( l+b) h

lateral surface area =2 (2+4) 6

lateral surface area=2 (6) 6

lateral surface area = 72 cm ²

( b )