Question

A cell's division time is $1$ minute. In $20$ minutes, a culture tube (culture medium) is $1/8^{th}$ filled with cells. When the tube will be fully filled?

• A. 21 minutes
• B. 23 minutes
• C. 60 minutes
• D. 160 minutes

Answer 1

Answer: (B)

In $20$ mins, culture tube is $1/8^{th}$ filled with cells. Each cell divides every minute producing two daughter cells.
Hence, in $21$ min $=\frac{1}{8}\times 2=\frac{1}{4}$
In $22$ min $\frac{1}{4}\times =\frac{1}{2}$
In $23$ min $\frac{1}{2}\times 2=1$
That means, in $23$ minutes, the culture tube will be completely filled.