A necklace weighs `50 g` in air, but it weighs `46 g` in water. Assume that copper is mixed with gold to prepare the necklace. Find how much copper is present in it. (Specific gravity of gold is `20` and that of copper is `10`.)

Explanation

To solve the problem of determining how much copper is present in the necklace, we will follow these steps:

### Step 1: Understand the given data
- Weight of the necklace in air (W_air) = 50 g
- Weight of the necklace in water (W_water) = 46 g
- Specific gravity of gold = 20
- Specific gravity of copper = 10

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