ML Aggarwal CBSE Solutions Class 8 Math 4th Chapter Cubes and Cube Roots Exercise 4.1
(5) (i) Volume of cuboid = 3 x 3 x 5
= 45 cm3
Therefore It is not a perfect cube.
We need grouping triplet to form a cube
The perfect cuboid should be = (3 x 3 x5) x (5 x 5 x 3)
(3 x 3 x 3) x (5 x 5 x 5)
∴ (5 x 5 x 3) = 75 cuboid should be needed to form a perfect cube.
(ii) Surface area = 486 cm2
Let side of cuboid box = a
We know that,
6a2 = 486
Or, a2 = 486/6 = 81
or, a2 = 92
or, a = 9
Therefore side of cuboid box = 9 cm.
(7) (i) 125 = 53 => cube of odd number
(ii) 512 = 83 = cube of even number
(iii) 1000 = 103 = cube of even number
(iv) 2197 = 133 = cube of odd number
(v) 4096 = 163 = cube of odd number
(vi) 6856 = 193 = cube of even number
(8) (i) 1531 = its cube ends in 1
(ii) 2358 = its cube ends in 2
(iii) 419 = its cube ends in 9
(iv) 4025 = its cube ends in 5
(v) 254 = its cube ends in 4
(vi) 987 = its cube ends in 3
(vii) 6752 = its cube ends in 8
(viii) 93 = its cube ends in 7
