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In 2020, a country had approximately 100,000 hectares of forests. Every decade, it is estimated that the number of hectares of forests will decrease by 20%. In order to slow down this deforestation, a non-governmental organisation (NGO) has decided to plant 3,000 hectares of trees every decade.

1. How many hectares of forests will there be in 2030? 2040?
2. Here is a function written in Python ($n$ is the number of decades):
  
def forest(n):
h = 100000
for k in range(n):
h = h * 0.8 + 3000
return h


1. Explain the algorithm.
2. Run the algorithm step by step for $n = 3$
3. Complete the following algorithm to find the year when the number of hectares of forests will go below 30,000 for the first time. Explain.
  
def year():
n = 0
h = 100000
while h ...
n = n + ...
h = ...
return 2020 + ...



## Vocabulary

• decade: a decade is ten years