Question

Eight small cubes each with an edge of 2cm are glued together to form a bigger cube as shown.

Another small cube with an edge of 2cm is glued at the centre on top of the bigger cube.

If the cost of painting is Rs 6/sq.cm, then what would be the cost of painting this new shape?


My Attempt so far
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Eight cubes of edge 2 cm are glued together.


So, the length of cuboid would become = 8 × 2 = 16 cm


Height and breadth would be the same i.e., 2 cm each


We know that, total surface area of the cuboid = 2(lb + bh + lh)


=2(16*2 +2*2+16*2) = 2(32+4+32) = 2(68)=136 sq.cm


Surface Area of the smaller cube = 6*side2 = 6*22=6*4=24 sq.cm


Total area = 136+24 sq. cm = 160 sq.cm


Cost of painting at Rs 6/sq.cm = 160*6 =Rs 960/-


But the answer is Rs 672/-

Answer 1

Answer:

There are totally 9 small cubes including the cube on the top so do the same calculation by substituting 9 in place of 8