Question

A rat passes through into a cubical piece of cheese 15cm once from top to bottom and then from left to right exactly through the middle of piece making a way of cross section 4*4 cm. Find TSA of remaining solid?

Answer 1

Tsa=6a^2= 225 × 6=1350

hole area = 2×4×4=32

extra hole sa= 4×15×4=240

So new tsa=1350-32+240=1558

Answer 2

area of outer surfaces = Total outer surface area - area of holes at surfaces

= 15×15×6 - (4×4×4)

=1350 - 64

= 1286 sq-cm

the cube has a junction at the centre of size 4×4×4 cubic-cm

effective length of hole excluding the cubicle junction = 15-4 =11 cm

CSA of the holes = 2 (11×4×4) = 352 sq-cm

Surface area at junction of holes = 2(4×4) = 32 sq-cm

So, TSA = 1286 + 352 + 32 = 1670 sq-cm....