Question

Three iron small cubes with sides 3 cm., 4 cm. and 5 cm respectively are melted and cast into a big cube. What is the ratio of total surface areas of sum of three cubes and a big cube ?

Answer 1

$v(cube \: \: 1) \: = l {}^{3} \\ = 3 \times 3 \times 3 \\ = 27cm {}^{3} \\ \: similarly \\ \\ v(cube \: 2) = 64 {cm}^{3} \\ \\ v(cube \: 3) = 125 {cm}^{3} \\ \\ v \: big \: cube = v1 + v2 + v3 \\ = 216 \\ \\ v \: big \: cube = l {}^{3} \\ 216 = l {}^{3 } \\ l = 6 \\ solve \: ahead$