Three cubes of metal with edges 3cm, 4 cm and 5 cm respectively are melted to form a single cube. The lateral surface area of the new cube formed is

Options

A. `72 cm^(2)`
B. `144 cm^(2)`
C. `128 cm^(2)`
D. `256 cm^(2)`

Answer

B

Explanation

Volume of new cube formed `= (3^(3) + 4^(3) + 5^(3)) cm^(3)`
`= (27 + 64 + 125) cm^(3) = 216 cm^(3)`
Let `a^(3) = 216 = 6^(3)`. Then, a = 6 cm
Lateral surface area of the new cube `= 4a^(2) = (4 xx 6 xx 6) cm^(2) = 144 cm^(2)`