You are given
.. longest piece : shortest piece = 3 : 1
Then
.. longest piece : total length = 3 : (3 +1) = 3 : 4
or
.. (longest piece)/(total length) = 3/4
.. longest piece = (total length)*(3/4)
.. = (9.4 m)*(3/4)
.. = 7.05 m
.. ≈ 7.1 m . . . . . . rounded to the nearest tenth meter