# Cells, growing old

Biology Level 4

In conditions of abundant food supply, bacteria like Escherichia coli and Pseudomonas aeruginosa reproduce by dividing into two identical daughter cells at regular intervals $$T_d$$, referred to as their doubling time. Assume that a large number of E. coli are growing in a batch culture with abundant food supply and that they've reached a steady state, i.e. the fraction of cells that are $$x\%$$ of a doubling time old, $$\displaystyle\phi_x$$, is constant in time. To the nearest minute, what is the age of the average cell if the doubling time is 60 minutes?

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