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Compare Lengths in cm

Measurement · Class II

Two pencils of different lengths , which is longer?

12 cm
type a value
130
18 cm
type a value
130
Live values
  • Longer pencil (cm)18
  • Length difference (cm)6
Live readout
Longer pencil (cm)18
Length difference (cm)6
Pencil A (cm)12 cm
Pencil B (cm)18 cm

Formulas in this lab

  • Longer pencil (cm)
    max⁡(a,b)\max(a,b)
  • Length difference (cm)
    ∣a−b∣|a-b|
Tip: Line them up at one end and compare the tips!

Frequently asked questions

▶How do we compare lengths?

We place two objects side by side and check which one is longer. We can also measure each with a ruler in centimetres and compare the numbers. A pencil of 12 cm is longer than one of 8 cm.

▶How do I use this length compare lab?

Use the sliders to set the length of two pencils in cm. The lab draws both pencils to scale and tells you which is longer and by how much.

▶When do we compare lengths in real life?

When choosing the taller of two flower plants in your garden, or finding which ribbon is longer for a craft project. Even comparing the height of two friends uses the same idea.

▶Tip for using a ruler

Always start measuring from the 0 mark on the ruler, not from the edge. The mark where the object ends gives the length in cm. Read carefully so you do not miss a millimetre.