Status: Waiting for your answer. Formula: Given: There are 5 cells of a rhizobium japonicum colony.This colony has a double rate of 6.7 hours within an optimum medium. Find: Use the formula above to calculate the time it would take for the given colony to grow to 300000 cells within an optimum medium. Calculate the solution for 't' to the nearest tenth using logarithms. Solution: t = hours