Parikshit makes a cuboid of plasticine of sides 5 cm, 2 cm, 5 cm. How many such cuboids will he need to form a cube?

Dimension of cuboid given = 5 x 5 x 2 cm

Volume of 1 cuboid = 5 x 5 x 2 = 50 cm³

Let the volume of the cube to be formed from given cuboids = x cm³

Now we know that this value x will be a perfect cube 

Number of cuboids x Volume of 1 cuboid = Volume of cube

Thus we can see that we have to multiply volume of 1 cuboid such that the resulting number is a perfect cube.

Thus, 50 x (Some number) = Perfect cube

50 × (x) = 1000

we know that the closest number is 20, such that 1000 is the perfect cube.

Therefore, Number of cuboids needed = 20