A plate of food holds 20 bacteria. Each bacterium divides into two every 30 minutes…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A plate of food holds bacteria. Each bacterium divides into two every minutes.
- How many doublings happen in hours?
- How many bacteria are there after hours?
- After how many hours are there bacteria?
Need a reminder? The key ideaShow
A pathogen is an organism or virus that causes disease. Typhoid is caused by Salmonella typhi, pneumonia by Streptococcus pneumoniae and Haemophilus influenzae, and the common cold by rhinoviruses. Bacteria multiply by dividing in two, so after doublings the number is .
The worked solution
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.
Given. Start: bacteria. One doubling every minutes.
Plan. Count the doublings. Then multiply the start by once for each doubling.
Step 1. The doublings. hours is minutes. doublings.
Step 2. The number. bacteria.
Step 3. The time to reach . . So doublings are needed. The time is minutes, which is hours.
Answer: doublings; bacteria; hours.
Check. At hours the number is .
Watch out. A bacterial culture cannot double for ever. The food runs out, and the model holds only for the early hours.
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