Algebra
posted by Jon .
Simplify: (4m/5n^2)(n/2m)
A)(8m^25n^3)/10n^2m
B)(8m^2+5n^3)/10n^2m
C)(4mn)/(5n^22m)
D)2/5n^2
I chose C
4m/5n^2  n/2m
4m/5(n)^2  n/2(m)
C

You need to find a common denominator for the two fractions you are trying to subtract. Simplifying the problem:
A/B  C/D = (A*DC*B)/(B*D)
In this case,
A=4m
B=5n^2
C=n
D=2m
So, A*D=4m*2m=8m^2
C*B=n*5n^2=5n^3
B*D=5n^2*2m=10n^2m
Substituting this into the simplified equation gives:
(8m^25n^3)/(10n^2m) which is answer (A)
A clue to the correct answer is that (A) and (B) are only a little different, so it's probably one of them!