Problem (Please HELP AND EXPLAIN!!!)

Kyra, Tai, and Rodney all measure sections of a tree that fell over during the last thunderstorm. They have different measurement tools, so Kyra measures 4 feet, Tai measures 3.5 yards, and Rodney measures 50 centimeters. There are 12 inches per foot, 3 feet per yard, and 2.54 centimeters per inch. If Kyra wants the total length of the tree to the nearest inch, how long is the tree?

Why was it necessary to add the three separate measurements together?

Why couldn't you add the feet, yards, and centimeters together? Use at least 1 complete sentence.