Originally Posted by

**waleedrabbani** just need to get these questions out of the way, help is greatly appreciated.

first question.

The population of insects has been increasing exponentially by 15% per year how long will it take for the population to double.

*I take it i will need to create formule of something like y = (1.15)^x but how would i know what to set my y to as i am not given any initial population

let P = initial population ...

2P = P(1.15)^{t}

Second Question

a 50mg sample of cobalt 60 decays to 40mg after 1.6 minutes how long will it take the sample to decay to 5% of its initial amount

40 = 50 e^{1.6k}

solve for the decay constant, k , then sub in for k in the equation below ... solve for t

2.5 = 50e^{kt}