A coin is placed `10cm` in front fo a concave mirror. The mirror produces a real image that has diameter `4` times that of the coin. What is the image distance.

Explanation

To solve the problem step by step, we will use the mirror formula and the concept of magnification.

### Step 1: Understand the given data
- The object distance (U) is given as 10 cm. Since it is in front of the mirror, we take U as negative:
\[ U = -10 \, \text{cm} \]

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