CoachTo measure a quantity — a length, a mass, a duration, a temperature — is to count how many times its agreed unit fits into it, using an instrument built for the job. The result is always written as a number with its unit: , , . A number alone is a rumor; number-plus-unit is a measurement.
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Example 37.2 (The price of a missing unit)
“Add 3 of flour.” Grams? Spoonfuls? Cups? The cake’s fate hangs on the missing word. Real disasters have followed missing or mixed-up units — pilots have run out of fuel mid-flight because kilograms were confused with pounds. Professionals write the unit every time, without exception; from this chapter on, so do we.