Jackie climbed 2 trees that were 1/2 * 1000 feet = 500 feet tall each.
Jackie climbed a final tree that was 1000 + 200 feet = <<1000+200=1200>>1200 feet.
In total, the 4 trees Jackie climbed were 1000 feet + 500 feet + 500 feet + 1200 feet = <<1000+500+500+1200=3200>>3200 feet.
The average height tree that Jackie climbed was 3200 feet / 4 trees = <<3200/4=800>>800 feet tall.
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