If a: b = c : d then (ma + nc): (mb + nd) is equal to:

\(\frac{a+b}{b -a}\) \(\frac{c}{d}\) \(\frac{a+b}{b+d}\) \(\frac{c-a}{b-d}\)

\(\frac{c}{d}\)

Here, a: b = c : d, Put a = c and b = d in the eq., we get ⇒ (ma + nc) : (mb + nd) = (mc + nc) : (md + nd)                                      = c (m + n) : d (m + n)                                      = c : d or \(\frac{c}{d}\)