A strain ratio and original length recover the exact extension. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Strain and original length can be inverted to recover extension
The dimensionless strain 1 over 2 acts on original length 6 m to give extension 3 m. The length vector and extension vector are checked separately.
ΔL=ϵL0=21×6m=3m
Strain and original length can be inverted to recover extension
The dimensionless strain 1 over 3 acts on original length 12 m to give extension 4 m. The length vector and extension vector are checked separately.
ΔL=ϵL0=31×12m=4m
Strain and original length can be inverted to recover extension
The dimensionless strain 1 over 5 acts on original length 15 m to give extension 3 m. The length vector and extension vector are checked separately.