Two metallic cubes of volume 125 and 91 are melted and formed into a big new cube. What is the edge of the new formed cube ?

Given : Volume of two cubes-

             $V_{1 }=125 c{m}^3$

             $V_2=91 c{m}^3$

To find : the edge of newly formed cube

Solution : Let the required edge of the new cube be '$a$'

Volume of the new cube = $a^3$

Also volume of new cube = $125 + 91 =216 c{m}^3$

$\Rightarrow a^3 =216 c{m}^3$

$\Rightarrow a = \sqrt[3]{216}$ 

$\Rightarrow a=6 cm$

Hence, the correct option is option B.