If your counting in hours lambda is 2

Remember he caught exactly 1 fish in the first 30 minutes and then exactly 2 in the next 1:30. The odds of the first event are e^-1 The odds of the second are 4.5*e^-3. Poisson problems are tricky. You have to think carefully about how to translate the word problem into a conditional. Here there is a restriction on how he catches those 3 fish so it is not the same as just asking the odds of 3 fish in 2 hours.