Answer: 15 feet.
Explanation:
Ms. Castille is originally about 6ft tall.
But at 3:00pm, her shadow because 8 feet long,
This indicates an increase. The percentage increase will be
6 × x% = 8
6x = 8 × 100
6x = 800
x = 800 ÷ 6
x = 133.3%
This means that the shadow of the tree that is 20ft long has increased by 33.3%.
Therefore to find the original length of the tree,
100% of the tree should be x
133.33% of the tree is 20ft
Therefore,
x = (100 ÷ 133.33) × 20
x = 0.75 × 20
x = 15ft.