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Standard VII

Mathematics

Determination of Significant Digits in a Number

The length of...

Question

The length of a simple pendulum is determined by measuring the length of thread l by meter scale and radius of bob r by Vernier callipers. The effective length L is obtained by adding the two, i.e., $L = l + r .$ If $l = 102.4$ cm and $r = 2.24$ cm, how would you use quote L in proper significant figures?

104.64 cm

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104.6 cm

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105 cm

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1.0464 cm

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Solution

The correct option is B 104.6 cm
The significant digits are decided by the reading with least significant digits, which corresponds to least accurate measurement.
Here $l$ is the least accurate measurement, with accuracy upto 1 decimal place. Hence the final answer would be approximated to 1 decimal place after zero.

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The length of a simple pendulum is determined by measuring the length of thread l by meter scale and radius of bob r by Vernier callipers. The effective length L is obtained by adding the two, i.e., L=l+r. If l=102.4 cm and r=2.24 cm, how would you use quote L in proper significant figures?