Question

a culture of a certain bacteria doubles every hour. at 9:00 a.m, there were already 120 bacteria. which equation represents the number of bacteria, n, at 8:00 a.m? how many bacteria were there? (1 point)

2n = 120; at 8:00 a.m., there were 240 bacteria.

$\frac{n}{2}=120$; at 8:00 a.m., there were 60 bacteria.

2n = 120; at 8:00 a.m., there were 60 bacteria.

$\frac{n}{2}=120$; at 8:00 a.m., there were 240 bacteria.

Explanation:

Step1: Understand the growth relationship

The bacteria doubles every hour. So the number of bacteria at 9:00 a.m. is twice the number at 8:00 a.m. Let $n$ be the number of bacteria at 8:00 a.m. Then the number of bacteria at 9:00 a.m. is $2n$. Since there are 120 bacteria at 9:00 a.m., the equation is $2n = 120$.

Step2: Solve the equation for $n$

Divide both sides of the equation $2n=120$ by 2. We get $n=\frac{120}{2}=60$.

Answer:

C. $2n = 120$; at 8:00 a.m., there were 60 bacteria.