Three students measured the length of a needle with meter rod and recorded as : (i) 0.2145m (ii) 0.21m (iii) 0.214m Which one is a correct record ?
Correct answer: C. Only (iii)
- A. Only (i)
- B. Only (ii)
- C. Only (iii)
- D. Both (i) and (ii)
Explanation
A metre rod normally has a least count of 1 mm = 0.001 m, so a reading should be recorded to the nearest 0.001 m. Thus 0.214 m is appropriate; 0.2145 m claims an extra decimal place, while 0.21 m omits a measurable place. Students commonly choose (i) because they think writing more digits always gives greater accuracy.
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