Half litre each of three samples of  $H_2{O}_2$ labeled 10 vol, 15 vol, 20 vol. are mixed and then diluted with equal vol. of water calculate relative strength of resultant $H_2{O}_2$ solution.

$V.S=N\times 5.6$

10 volume of  ${\mathrm{H}}_2{\mathrm{O}}_2=\frac{10}{5.6}\mathrm{N}$

15 volume of  ${\mathrm{H}}_2{\mathrm{O}}_2=\frac{15}{5.6}\mathrm{N}$

20 volume of ${\mathrm{H}}_2{\mathrm{O}}_2=\frac{20}{5.6}\mathrm{N}$

Total volume of = 500 + 500 + 500 = 1500 ml

After dilution volume of solution = 3000 ml

$N=\frac{\frac{10}{5.6}\times 500+\frac{15}{5.6}\times 500+\frac{20}{5.6}\times 500}{3000}=\frac{4107.13}{3000}=1.369N$

$V.S=N\times 5.6=1.369\times 5.6=7.5$