help in maths 1013 (1 Viewer)

[HSC :(]

hey

i was wonderin if someone could help me in this question;

A colony of birds increases by 10% each year from birth and death processes, and by 20 birds a year by immigration. Initially there were 40 birds. How many are there after 5 years?

Thanx

 

[BlackJack]

It's nice to think of them this way:
For a particular year:
- assume the 20 immigrants are not going to participate in the birth/death process; they've only just arrived.
- So you incr. the resident population by 10%, multiply by 1.1
Hence, at the start of next year, there is:
(population this year)*1.1 + 20 birds.
Do this 5 times.