CBSE Class 8 Mathematics
Question 12 of 12
Proportional Reasoning 1 — Question 12
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Question The ₹ 10 coin is an alloy of copper and nickel called ‘cupro-nickel’. Copper and nickel are mixed in a 3 : 1 ratio to get this alloy. The mass of the coin is 7.74 grams. If the cost of copper is ₹ 906 per kg and the cost of nickel is ₹ 1,341 per kg, what is the cost of these metals in a ₹ 10 coin?
Ratio of copper and nickel in ₹ 10 coin = 3 : 1 Mass of one ₹ 10 coin = 7.74 grams ∴ Mass of copper in one ₹ 10 coin = \(\frac{3}{3+1}\) × 7.74 = \(\frac {3}{4}\) × 7.74 = 5.805 grams Mass of nickel in one ₹ 10 coin = \(\frac{1}{3+1}\) × 7.74 = \(\frac {1}{4}\) × 7.74 = 1.935 grams Cost of 1 kg copper = ₹ 906 ∴ Cost of 1000 grams of copper = ₹ 906 ∴ Cost of 5.805 grams copper = \(\frac {906}{1000}\) × 5.805 = ₹ 5.26 Cost of 1 kg nickel = ₹ 1341 ∴ Cost of 1000 grams of nickel = ₹ 1341 ∴ Cost of 1.935 grams nickel = \(\frac {1341}{1000}\) × 1.935 = ₹ 2.59 ∴ In one ₹ 10 coin, the cost of copper and the cost of nickel are respectively ₹ 5.26 and ₹ 2.59.