Strain is a ratio, so scaled extension-length pairs can land on the same value. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A scaled extension-length pair can give the same strain

Extension 1 m over original length 4 m gives strain 1 over 4.

ϵ=ΔLL0=1 m4 m=14\epsilon=\frac{\Delta L}{L_0}=\frac{1\ \text{m}}{4\ \text{m}}=\frac{1}{4}
Strain ratio scanLength and extension can scale together while strain stays fixed.original lengthextensionoriginalLength=4 mextension=1 mstrain=1/4

A scaled extension-length pair can give the same strain

Extension 2 m over original length 8 m gives strain 1 over 4.

ϵ=ΔLL0=2 m8 m=14\epsilon=\frac{\Delta L}{L_0}=\frac{2\ \text{m}}{8\ \text{m}}=\frac{1}{4}
Strain ratio scanLength and extension can scale together while strain stays fixed.original lengthextensionoriginalLength=8 mextension=2 mstrain=1/4

A scaled extension-length pair can give the same strain

Extension 3 m over original length 12 m gives strain 1 over 4.

ϵ=ΔLL0=3 m12 m=14\epsilon=\frac{\Delta L}{L_0}=\frac{3\ \text{m}}{12\ \text{m}}=\frac{1}{4}
Strain ratio scanLength and extension can scale together while strain stays fixed.original lengthextensionoriginalLength=12 mextension=3 mstrain=1/4