Volume strength of H2O2 is the volume of O2 released on decomposition of one volume of H2O2 at STP.
2H2O2→2H2O+O2
So, 2 moles of H2O2 gives 1 mole of O2
Therefore, 1 mole of H2O2 will give 11.2 L of O2 gas.
Volume strength of H2O2 at 1 atm, 273 K = M × 11.2
=8.9×11.2=99.68=100
Hence, answer is 100.