Hi Anonymous,

first of all - this is **not **a brain teaaser, but an ordinary **estimation question! **Here is a **high-level approach:**

I would start with the second question, because it is most straight forward:

1. Clarify the required generation capacity in France (a Gigawatt figure)

2. Clarify the generation capacity per square meter of solar panel

3. Divide 1 by 2

Regarding the first question:

1. Brainstorm a list of facilities where solar panels can be installed (of course roofs, but there might be additional areas)

2. Estimate a maximum percentage for each kind of installation facility that can be used for solar panel installations

3. Estimate the average installation area (in sqm) available for each facility type

4. Estimate the number for each facility type (e.g. number of roofs in France)

5. Multiply 4 with 3 and with 2 for each facility type and add up the results. This is the overall (potential) installation area of solar panels in France (in sqm). Since a panel has 1 sqm size, this is also the number of panels.

Cheers, Sidi