Three varieties of tea costing ₹120/kg, ₹150/kg and ₹200/kg are mixed in the ratio 2 : 3 : 5 by weight. Find the cost per kg of the resulting mixture.

Take weights 2 kg, 3 kg, 5 kg (total 10 kg). Total cost = 2×120 + 3×150 + 5×200 = 240+450+1000 = ₹1690. Cost per kg of mixture = 1690/10 = ₹169. Shortcut: the weighted average must lie between the lowest (120) and highest (200) price, and closer to 200 since it carries the largest weight (5) — ₹169 fits, while ₹175 is too high to be a valid weighted average here.