Let the frequency of the first fork be $f_1$ and that of second be $f_2$.
We then have, $f_1=\frac{v}{4 \times 24}$ and
$f _2=\frac{ v }{4 \times 25}$
We also see that $f _1 > f _2$
$\therefore f _1- f _2=6$
$\text { and } \frac{ f _1}{ f _2}=\frac{24}{25}$
Solving $(i)$ and $(ii)$, we get $f _1=150\,Hz$ and $f _2=144\,Hz$
(Useful information) : $\sqrt{167 R T}=640 j^{1 / 2} mole ^{-1 / 2} ; \sqrt{140 RT }=590 j ^{1 / 2} mole ^{-1 / 2}$. The molar masses $M$ in grams are given in the options. Take the value of $\sqrt{\frac{10}{ M }}$ for each gas as given there.)
$Y = A\sin (100t)\cos (0.01x)$
where $Y$ and $A$ are in millimetre, $t$ is in seconds and $x$ is in metre. The velocity of wave is ..... $m/s$