Question

three cubes of side 3cm,4cm and 5cm respectively are melted to form a new cube . what is the side of new cube? fast its urgent

Answer 1

Total volume of cubes = 216 cm 
so that 6 is the side of new cube

Answer 2

If three cubes are melt to form new cube then also there volume remains the same.

So, Let the side of new cube be x

By condition,

$x {}^{3} = 3 {}^{ 3} + 4 {}^{3} + 5 {}^{3} \\ x {}^{3} = 27 + 64 + 125 \\ x {}^{3} = 216 \\ x = 6$
Therefore side of new cube formed = 6cm