Question

UNIT
Find the area to be painted in the following block with a cylindrical
hole. Given that length is 15 cm. width 12 cm, height 20 em and
radius of the hole 2.8 cm.
20 cm
15 cm
12 cm​

Answer 1

Total surface Area of the block= 2(lb+bh+lh),

= 2(15×12+12×20+20×15),

= 2(180+240+300),

= 2(720),

=1440 cm².

But, there is a hole, which is opened both sides of the Cuboid, which means that it effects both the faces of the block,

then, area of the circle = π r²,

= 22×28×28/7×100,

= 2464/100 cm²,

= 24.64 cm².

So, area to be painted = (1440- 24.64) cm²,

= 1415.36 cm².

NOW, THAT'S THE CORRECT ANSWER.