At what distance in front of a concave mirror of focal length 10 cm, an object be placed so that its real image of size five times that of the object is obtained?

Explanation

To solve the problem step by step, we need to find the object distance (u) for a concave mirror with a focal length (f) of 10 cm, such that the real image formed is five times the size of the object.

### Step-by-Step Solution:

1. **Identify Given Values:**
- Focal length of the concave mirror, \( f = -10 \) cm (negative because it is a concave mirror).
- Magnification, \( M = -5 \) (negative because it is a real image and the image is inverted).

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