50 kg of an alloy of lead and tin contains 60% lead. How much lead must be melted into it to make an alloy containing 70% lead?

Explanation

To solve the problem step by step, we will follow these calculations:

### Step 1: Calculate the amount of lead in the initial alloy
The initial alloy weighs 50 kg and contains 60% lead.

\[ \text{Amount of lead} = \frac{60}{100} \times 50 = 30 \text{ kg} \]
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