Shren A.C.

Petr Petrovich and Ivan Ivanovich were traveling together on a train. Each of them first looked out the window, then read a newspaper, then solved a crossword puzzle, and finally drank tea. Only for Petr Petrovich, each subsequent activity took twice as long as the previous one, while for Ivan Ivanovich, it took four times as long. They started looking out the window at the same time and finished drinking tea at the same time as well. What was Petr Petrovich doing when Ivan Ivanovich started the crossword puzzle?
Let Pyotr Petrovich look out the window for $x$ minutes, and Ivan Ivanovich for $y$ minutes. Then $x+2x+4x+8x=y+4y+16y+64y$, which means $15x=85y$. Ivan Ivanovich started solving the crossword after $5y=15x/17$ minutes. This is less than $x$, so Pyotr Petrovich was looking out the window at that time.