Q. If a : b = c : d = e : f = 1 : 2, then (3a + 5c + 7e) : (3b + 5d + 7f) is equal to:
Answer: 1 : 2
Notes: $latex \frac{a}{b} = \frac{c}{d} = \frac{e}{f} = \frac{1}{2}&s=1$ $latex \therefore \frac{3a}{3b} = \frac{5c}{5d} = \frac{7e}{7f} = \frac{1}{2}&s=1$ $latex \therefore \frac{3a+5c+7e}{3b+5d+7f} = \frac{1}{2} = 1 : 2&s=1$ Hence option [A] is the right answer

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