Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
Sanjay steps a logistic population with per hour, cells and cells, for hours. With a time step of h his program reports cells at h. With h it reports cells. Which answer is wrong, and why? What does the exact formula give?
Logistic growth: . An Euler step: N = N + r * N * (1 - N / K) * dt. Exact curve: . It reaches at , where it grows fastest, at .
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The wrong answer. cells is above cells, which a logistic population never passes. The step of h is larger than h, so each step jumps too far and overshoots.
Step 2. Exact. cells.
Step 3. The small step. With h the stepped count agrees with the exact one to two decimal places.
Answer: cells is wrong; the exact count is cells. Keep much smaller than .
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