Question 1123615
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Both of the responses you have received so far are valid; and they demonstrate general methods for solving problems like this.<br.
But with the given information, you don't need logarithms or exponential functions.<br>
The given information tells you the factor by which the population increased between 10 minutes and 20 minutes; the population increased by the same factor in the first ten minutes.<br>
1357/628 = 2.160828....
628/2.160828 = 290.629...<br>
To the nearest whole number, the initial population was 291.