Q. If a : b : c = 7 : 3 : 5, then (a + b + c) : (2a + b - c) is equal to :
Answer: 5 : 4
Notes: $latex a : b : c = 7 : 3 : 5$ $latex => \frac{a}{7} = \frac{b}{3} = \frac{c}{5} = k (let)$ $latex => a = 7k, b = 3k, c = 5k$ Now $latex (a + b + c) : (2a + b - c)$ $latex = (7k + 3k + 5k) : (2\times 7k + 3k - 5k)$ $latex = 15k : 12k = 5 : 4$ Hence option [D] is correct answer.

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