Two flag posts of height 13 m and 18 m are erected 21 m apart. Find l, the length of the string (in metres) needed to join the tops of the two posts, correct to one decimal place.
Please directly answer the question and provide the final value, e.g., 1, 2.5, 300.
Question: Two flag posts of height 13 m and 18 m are erected 21 m apart. Find l, the length of the string (in metres) needed to join the tops of the two posts, correct to one decimal place.
Please first conduct reasoning, and then answer the question and provide the final value, e.g., 1, 2.5, 300, at the end.
Question: Two flag posts of height 13 m and 18 m are erected 21 m apart. Find l, the length of the string (in metres) needed to join the tops of the two posts, correct to one decimal place.