The contribution in the total current flowing through a semiconductor due to electrons and holes are $\frac{3}{4}$ and $\frac{1}{4}$ respectively. If the drift velocity of electrons is $\frac{5}{2}$ times that of holes at this temperature, then the ratio of concentration of electrons and holes is

6 : 5

As we know current density J = nqv

$⇒ J_e=n_eqv_e$ and $J-h=n_hqv_h$

$⇒\frac{J_e}{J_h}=\frac{n_e}{n_h}×\frac{v_e}{v_h}$

$⇒\frac{3/4}{1/4}=\frac{n_e}{n_h}×\frac{5}{20}⇒\frac{n_e}{n_h}=\frac{6}{5}$