To find the number of bacteria at 8:00 a.m. when we know that the number of bacteria doubles every hour, we can set up the equations based on the information given at 9:00 a.m.
At 9:00 a.m., there are 120 bacteria. This means that at 8:00 a.m. (one hour earlier), there were half as many bacteria because it doubles every hour.
The equation that represents the number of bacteria at 8:00 a.m. can be written as:
\[ n/2 = 120 \]
Where \( n \) is the number of bacteria at 9:00 a.m. So, to find the number of bacteria at 8:00 a.m., we can rearrange this equation to find \( n \):
To find \( n \) (the number of bacteria at 9:00 a.m.), we multiply both sides by 2:
\[ n = 120 \times 2 = 240 \]
Thus, at 8:00 a.m., there were 240 bacteria.
Now looking at the options provided:
- A. \( n/2 = 120 \) at 8:00 a.m., there were 240 bacteria ✅ Correct
- B. \( 2n = 120 \) at 8:00 a.m., there were 60 bacteria ❌ Incorrect
- C. \( 2n = 120 \) at 8:00 a.m., there were 240 bacteria ❌ Incorrect (the equation is incorrect)
- D. \( n/2 = 120 \) at 8:00 a.m., there were 60 bacteria ❌ Incorrect
The correct answer is A. At 8:00 a.m., there were 240 bacteria.
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