You and a friend want to know how much rope you need to climb a large rock. your friend is 5.5 feet tall and casts a shadow that is 18 feet long. if the rock casts a shadow that is 209.5 feet long, calculate the height of the rock from the ground. round your answer to the nearest foot. (hint: make a drawing)

64 ft
18 ft
210 ft
219 ft

The concept that is useful in order to answer this item is the concept of ratio and proportion. Let x be the height of the rock from the ground. We use the equation below to answer.
                                    5.5 ft / 18 ft = x ft / 209.5 ft
The value of x from the equation is 64 ft. Thus, they will be needing approximately 64 ft of rope.

The first answer is correct