Number of thermosetting polymers out of the following is ______ .
Bakelite, polythene, polystyrene, melamine, PVC,urea-formaldehyde, teflon

Explanation

To determine the number of thermosetting polymers from the given list, we will analyze each polymer one by one:

1. **Bakelite**: This is a thermosetting polymer. It is formed by the polymerization of phenol and formaldehyde and cannot be remolded or softened upon heating.

2. **Polythene**: This is a thermoplastic polymer. It can be melted and remolded multiple times, so it is not a thermosetting polymer.

3. **Polystyrene**: This is also a thermoplastic polymer. Like polythene, it can be melted and reshaped, thus it is not a thermosetting polymer.

4. **Melamine**: This is a thermosetting polymer. It is often used in the production of laminates and can’t be remolded once set.

5. **PVC (Polyvinyl Chloride)**: This is a thermoplastic polymer. It can be reshaped upon heating, so it is not a thermosetting polymer.

6. **Urea-formaldehyde**: This is a thermosetting polymer. It is commonly used in adhesives and finishes and cannot be remolded after it has set.

7. **Teflon**: This is a thermoplastic polymer. It can be melted and reshaped, so it is not a thermosetting polymer.

Now, let's summarize the findings:

- Thermosetting polymers identified: Bakelite, Melamine, Urea-formaldehyde.
- Total number of thermosetting polymers = 3.

Therefore, the answer is: **3**.

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