Question 1019465
Given that 
{{{f/n=g/m}}}
we can multiply by n to find
{{{f = (g*n)/m}}}
Now plug in to get
f = (8.1)(2.5) / 16.25 = 1.246
or, in fractions
f = (8 1/10)(2 1/2) / (16 1/4)
Now 16 1/4 = 65/4 so that
f = (81/10)(5/2)(4/65) = 1620/1300 = 162/130 = 81/65