Answer:
1,000,000,000 leaves or 1 x 10^9 leaves
Step-by-step explanation:
One large oak tree has 2 x 10^5 leaves, so we can make that number to 200000
There are 5 x 10^3 oak trees in a forest, we can make that number to 5000
Since we want to find out how many leaves are in the whole forest we multiply: 200000 x 5000 = 1,000,000,000
So approximately there are 1 billion leaves or 1 x 10^9 leaves