The best CAPTCHA ever - 2
I already wrote about The best CAPTCHA ever — it’s a simple, but impressive looking math expression. Use of a scientific CAPTCHA is taking off. Now you can see one on the registration page of the library of Moscow Institute of Physics and Technology:
Translation:
In order to launch the registration process, please pass a quick test. It has only one school-level problem.
You need to determine the resistance between the points A and B in the circuit.