A student is performing an experiment using a resonance column and...

$v = 0.35, \lambda = 4\gamma$

$v = \lambdaf = 0.35 \times 4 \times 244 ≅ 340m{s}^{2}$

$v = \dfrac{1}{4\gamma}\sqrt{\dfrac{\gammaRT}{M}}$

$v = \sqrt{\dfrac{\gammaRT}{M}} ⇒ M = \dfrac{\gammaRT}{{v}^{2}}$

For monoatomic gas : $\gamma = 1.67 ⇒ M = \dfrac{{640}^{2}}{100} \times \dfrac{1000}{{340}^{2}}$

$\approx {\left({M}^{2} - \dfrac{1}{17}\right)}^{2}$

$\approx 36$

$M = 36$