At the end of 2018, the tree will grow 100 x 10/100 = <<100*10/100=10>>10 meters more.
Thus, its height at the end of 2018 is 100 + 10 = <<100+10=110>>110 meters.
At the end of 2019, the tree will grow 110 x 10/100 = <<110*10/100=11>>11 meters more.
So, its height at the end of 2019 is 110 + 11 = <<110+11=121>>121 meters.
Therefore, the tree has grown 121 - 100 = <<121-100=21>>21 meters.
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