Answer
(a) For air, $c=343 \frac{\mathrm{m}}{\mathrm{s}}$
(b) For helium, $c=1010 \frac{\mathrm{m}}{\mathrm{s}}$
(c) For natural gas, $c=446 \frac{\mathrm{m}}{\mathrm{s}}$
Work Step by Step
$$
c=\sqrt{k R T}
$$ $$
T=293 \mathrm{~K}
$$ (a) For air, $c=\sqrt{(1.40)(286.9)(293)}=343 \frac{\mathrm{m}}{\mathrm{s}}$
(b) For helium, $c=\sqrt{(1.66)(2077)(293)}=1010 \frac{\mathrm{m}}{\mathrm{s}}$
(c) For natural gat $c=\sqrt{(1.31)(518.3)(293)} \left\lvert\,=446 \frac{\mathrm{m}}{\mathrm{s}}\right.$
