  Asteroseismology offers the possibility of probing stellar interiors and
testing evolutionary and seismic models. Precise photometry and spectroscopy
obtained during multi-site campaigns on young open clusters allows discovering
rich samples of pulsating stars and using them in a simultaneous seismic
modelling called ensemble asteroseismology. The aim of this study is to obtain
the age of the open cluster NGC 6910 by means of ensemble asteroseismology of
the early-type pulsating members, to derive their stellar parameters, and to
classify the excited modes. We used time-series analysis, performed photometric
and spectroscopic mode identification, and calculated grids of evolutionary and
seismic models to apply the procedure of ensemble asteroseismology for nine
pulsating members of NGC 6910. With two iterations of the procedure of ensemble
asteroseismology applied to nine pulsating stars we derived an age of
10.6$^{+0.9}_{-0.8}$ Myr for NGC 6910. Of the nine pulsating stars examined in
the paper, eight are $\beta$ Cep stars, including three that are hybrid $\beta$
Cep and slowly pulsating B-type (SPB) pulsators, and one is an SPB star.
Interestingly, the least massive $\beta$ Cep star, NGC 6910-38, has a mass of
about 5.6 M$_\odot$. The present theory does not predict unstable $p$ modes in
B-type stars with such a low mass. The $g$ modes with relatively high
frequencies ($>3.5$ d$^{-1}$), observed in three members of the cluster, are
also stable according to seismic modelling. Both findings pose a challenge for
theoretical calculations and prompt a revision of the opacities. The procedure
of ensemble asteroseismology was found to be successful for NGC 6910 and $\chi$
Per on the basis of pulsating B-type stars and can therefore be applied to
other young open clusters that are rich in such stars.
