First, we would add 55 feet to 21 feet to get the total amount of feet that it fell, which is equal to 76. Next, we would divide that by 2 to get half of the height that it fell, which would equal 38. Because 38 is under 55, we know that it is still above the lake. So from here, we would subtract 55 and 38 to get 17 feet above the lake. 17 feet above the lake should be your answer.
