Physics exercise from the group 4

I will give you a simple exercise, a physic exercise and I hope you will find rapidly this simple exercise.

So, imagine. You do a travel in Paris. So, you visit the eiffel tower. You go up the staircases to the first floor and next, to the second floor. Then, after the visit, you will ask a question : «  What distance separate the ground and the first floor ? And the second floor ?  »

To resolve this problem, you need a straightedge, only a straightedge. And, also, a little index, you must be remote of the Eiffel Tower and you must know the distance between you and the the famous tower.

Before to give you some measure, I want you find how to make.