If the cell cycle lasts 36 hours and mitosis takes 25% of the cell cycle, how many hours will the cell be in mitosis?

Mitotic index I = (P+M+A+T)/ TOTAL cell, N) *100 %
(P+M+A+T) — the sum of all cells in phase as prophase, metaphase, anaphase and telophase, respectively; N — total number of cells.
Mitototic index (MI) is 3/25000 x 100 = 1.2 %
From the cell cycle, 1.2% is mitotic and the rest will obviously be interphase.
So, 1.2% is 30 minutes, so 100% (length of total cell cyle) is 2500 minutes (42hours).

I hope this helped you.