Reading a Measuring Scale
Most people read a scale by counting the little lines. That works right up until the little lines are not worth one.
Show meWorked example — Reading a Measuring Scale
Watch it done once
A measuring cylinder. Two numbered marks, 40 and 60, with four gaps between them. The liquid sits one small mark above 40. How much is there?
- Find two NUMBERED marks and subtract: 60 − 40 = 20.
Never start at the small marks. Start where the instrument tells you the truth in writing.
- Count the GAPS between them, not the lines: four.
Gaps are what carry the value. Counting lines is where almost every wrong reading is born.
- Divide: 20 ÷ 4 = 5. One small mark is worth 5.
This is the only number you actually needed, and the instrument never printed it.
- One mark above 40 is 45.
Not 41 — which is what counting lines would have told you.
Answer45
The idea — Reading a Measuring Scale
Before you read any scale, work out what one mark is worth. The instrument never prints that number.
You did not memorise instruments. You got fast at one question you can ask any of them.
Questions about Reading a Measuring Scale
How do you read a measuring scale correctly?
Find two numbered marks, subtract them, then divide by the number of gaps between them to get the value of one small mark.
Should you count lines or gaps on a scale?
Count the gaps, not the lines — gaps are what carry the value, and counting lines is where most wrong readings come from.
In the example with marks 40 and 60 and four gaps, what is one small mark worth?
60 minus 40 is 20, divided by 4 gaps equals 5, so one small mark is worth 5.
What is the final reading when the liquid sits one mark above 40?
The reading is 45, not 41 — because each mark is worth 5, not 1.
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