A concave lens has focal length of `20 cm`. At what distance from the lens a 5 cm tall object be placed so that it forms an image at `15 cm` from the lens? Also, calculate the size of the image formed.

Explanation

To solve the problem, we will use the lens formula and the magnification formula. Let's go through the steps one by one.

### Step 1: Identify the given values
- Focal length of the concave lens (F) = -20 cm (negative because it is a concave lens)
- Image distance (V) = -15 cm (negative because the image is virtual and on the same side as the object)
- Height of the object (h₀) = 5 cm

### Step 2: Use the lens formula
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