Find the length of the polyline MNP if MN = 6.3 dm and NP is 2.8 dm greater than MN.

Let us determine to what number of decimeters the length of the NP link, which belongs to the broken MNP, corresponds to the number of decimeters, knowing by the problem statement that the length of the NP link is 2.8 decimeters longer than the length of the MN link:

6.3 + 2.8 = 9.1.

Let us determine to what number of decimeters the length of the broken MNP corresponds, knowing by the condition of the problem that it consists of only two links MN and NP:

6.3 + 9.1 = 15.4.

Answer: The length of the broken MNP is 15.4 decimetres.