SOLUTION: If a:b=c:d, then (ma+nc)/(mb+nd) is equal to ?.

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Question 1095606: If a:b=c:d, then (ma+nc)/(mb+nd) is equal to ?.
Answer by math_helper(2461) About Me  (Show Source):
You can put this solution on YOUR website!
a:b = c:d —> a/b = c/d —> a/b = k (and also c/d = k)
a/b = k —> a=bk —> ma = mbk
c/d = k —> c =dk —> nc = ndk
Now take
++%28ma%2Bnc%29+%2F+%28mb%2Bnd%29+
and substitute for 'ma' and 'nc':

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Ans: ++highlight%28%28ma%2Bnc%29+%2F+%28mb%2Bnd%29++=+a%2Fb+=+c%2Fd%29+
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Check: Say a/b = c/d = 3
now if a=6, b=2 and c=21, d=7 we get (m & n can be left symbolic):