A group of biology students are assisting a researcher from the University of Toronto on a project.

A group of biology students are assisting a researcher from the University of Toronto on a project. They are trying to determine the growth rate of frogs in a marsh near Owen Sound.  There are 200 frogs in the first year.  By the time the students are in grade 12, 40 frogs were born, 90 died and 5 frogs immigrated. Determine the growth rate.

This is my attempt. I used this formula:

[(births + immigration)] – (death + emigration)]/initial population size x 100%

= [(40+5) - (90+0)]/200 x 100%
= -45/200 x 100%
= -0.225 x 100%
= -22.5%

Probably a dumb question but can you have a negative rate of change? I don't feel like it's right...
Should I have used the formula λ  = N (t + 1)/N (t) instead?

Thank you so much for the help!