Given- 90% of runner completed the marathon.
out of which 30% are man.
To proof - let the total number of runner be y.
the men completed the marathon be 30% of the 90%.
thus we have
30% of 90% of y = 270
[tex]\frac{30}{100}[/tex]×[tex]\frac{90}{100}[/tex]×y = 270
now solving the above equation
we get
[tex]\\y=\frac{270\times 100\times 100}{90\times 30}[/tex]
Thus solving the equation
y = 1000
Thus the total runners of men who completed marathon be 1000.
Hence proved
