There are currently 21 frogs in a (large) pond. the frog population grows exponentially, tripling every 7 days. how long will it take (in days) for there to be 150 frogs in the pond?

Let x =  number of days

The initial number of frogs  = 21.
The number of frogs triples every 7 days.
The exponential function that models the number of frogs with respect to the number of days is


When the population is 150, then

A graph of y versus confirms the answer.

  12.5 days