If velocity of light $c$, Planck’s constant $h$ and gravitational constant $G$ are taken as fundamental quantities, then express time in terms of dimensions of these quantities.

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$T = kc ^{ x } h ^{ y } G ^{ z }$

${\left[M^{0} L^{0} T\right]=\left[L^{-1}\right]^{x} \times\left[M L^{2} T^{-1}\right]^{y} \times\left[M^{-1} L^{3} T^{-2}\right]^{z}}$

$=\left[M^{y-z} L^{x+2 y+3 z} T^{-x-y-2 z}\right]$

Comparing powers

$y-z=0$

$x+2 y+3 z=1$

$-x-y-2z=1$

$y =\frac{1}{2}, z =\frac{1}{2}, x =-\frac{5}{2}$

$T = kc ^{-\frac{5}{2}} h ^{\frac{1}{2}} B ^{\frac{1}{2}}$

$T =k \sqrt{\frac{h G}{c^{5}}}$

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