Concept 5 of 8Foundation
Watch on YouTubeVideoMeasuring length correctly
Rules for a good measurement:
- Put the ruler tightly along the edge of the object.
- Start from the 0 mark. If 0 is damaged, start from any whole number and subtract.
- Look straight down at the mark — not from an angle (avoid parallax error).
- Record with units (cm or mm).
For curved lines (road on a map): lay a thread along the curve, then straighten and measure the thread.
Example
Measuring a pencil with ruler broken at 0: align at 2 cm, tip at 15.4 cm → length = 15.4 – 2 = 13.4 cm.
💡 Tip:Parallax = reading shifts when seen from different angles. Always view perpendicular.
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5 questions to check what you just read.
0 / 5
- Q1.Parallax error occurs when:
- Q2.Pencil tip at 15.4 cm, other end at 2 cm mark. Length:
- Q3.Best way to measure a curved road on a map:
- Q4.When reading a ruler, look:
- Q5.If a ruler's 0 mark is worn, you can: