NTSE Stage 2 SAT 2017 Question Paper

Let length, breadth and height of solid brick be x units, 2x units and 3x units.
Volume = Number of brick
$=\mathrm{L}\times \mathrm{B}\times \mathrm{H}$4
$=\mathrm{x}\times 2\mathrm{x}\times 3\mathrm{x}$
$=6{\mathrm{x}}^2$
Now let $\mathrm{x}=1,6\times {\left(1\right)}^3=6$
at x = 2, $6\times {\left(2\right)}^3=48$
at x = 3, $6\times {\left(3\right)}^3=222$
at x = 4, $6\times {\left(4\right)}^3=384$
at x = 5, $6\times {\left(5\right)}^3=750$
Hence, at x = 5, number of cubes are going above 400.