Question

Three cubes, each of side 8 cm, are joined together side by side. Find
the total surface area of the resulting cuboid.

Answer 1

If three cubes of side 8 cm are joined together side by side, 
dimensions of resulting cuboid are
length = 8*3 = 24 cm
breadth = 8cm
height = 8cm

TSA = 2(lb+bh+lh)
       = 2(24×8+8×8+24×8)
       = 2(192+64+192)
       = 2×448
       = 896 cm²

Answer 2

Given that, three cubes of side 8 cm are joined side by side.

The dimensions of the resultant cuboid are:
Length = 8 + 8 + 8 = 24 cm
Breadth = 8 cm
Height = 8 cm

Total surface area of cuboid = 2(LB + BH + HL)
                                              = 2 [(24*8) + (8*8) + (8*24)]
                                              =  2[192 + 64 + 192]
                                              = 2[448]
                                              = 896
Total surface area = 896 sq cm.