Question

A cuboidal box of dimensions 1m x 2m x 1.5m is to be painted except its bottom .Calculate how much area of the box has to be painted ?​

Answer 1

Answer:

Length of cabinet(l)  = 2 m, Breadth of(b) = 1 m

Height of cabinet (h)= 1.5 m

 Surface area of cabinet= area of top + lateral surface area

= lb + 2(l+b)h

 Surface area of cabinet= lb + 2(l+b)h

= 2×1+2(2+1)×1.5

= 2+2(3)× 1.5

= 2+ 6 ×1.5

= 2+ 9

= 11 m²

Hence, the required surface area of cabinet is 11m²

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Answer 2

Given :

Length of cuboid (l) = 1 m

Breadth of cuboid (b) = 2 m

Height of cuboid (h) = 1.5 m

To Find :

Area of the box that has to be painted.

Some important formulae :

Total surface area of cuboid = 2(lb+bh+hl)

Lateral surface area of cuboid = 2h(l+b)

Solution :

Area of bottom of cuboid = l×b

= 1×2

= 2 m²

And,

Total surface area = 2(lb+bh+hl)

= 2(1×2+2×1.5+1.5×1)

= 2(2+3+1.5)

= 2×6.5

= 13 m²

According to the question the bottom of the box is not painted, then

Area of box painted = (Total surface area - bottom area)

Area of box painted = (13 - 2) m² = 11 m².

Therefore, 11 m² of area of box is painted.