Three students measured a needle with a metre rule and recorded (i) 0.2145 m, (ii) 0.21 m and (iii) 0.214 m. Which record is correct?
Correct answer B. Only (iii)
Explanation
A metre rule has a least count of 1 mm, or 0.001 m, so a reading should be given to three decimal places in metres, as in 0.214 m.
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