A culture of a certain bacteria doubles every hour. At 9:00 am there’s we’re already 120 bacteria. Which equation represents the number of bacteria, n, at 8:00 am! How many bacteria were there?

Question

A: n/2 = 120; at 8:00, there were 240 bacteria.
B: 2n = 120; at 8:00 am, there were 60 bacteria.
C: n/2 = 120; at 8:00 am, there were 60 bacteria.
D: 2n = 120; at 8:00 am, there were 240 bacteria.

Answer 1

The correct equation is C: n/2 = 120.
To find the number of bacteria at 8:00 am, we need to go back in time by 1 hour. Since the culture doubles every hour, we need to divide the number of bacteria at 9:00 am (which is 120) by 2 to find the number at 8:00 am. Thus, the number of bacteria at 8:00 am is 120/2 = 60.
Therefore, the correct answer is: at 8:00 am, there were 60 bacteria.