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Question:

The respective number of significant figures for the numbers 23.023, 0.0003 and 2.1×10⁷ are:

5, 1, 2

5, 5, 2

5, 1, 5

4, 4, 2

Solution:

Zeroes before a digit is not counted as a significant figure. In the first number, all digits are significant. In the second number, only 3 is significant; all other zeroes are before the digit and therefore not counted as a significant figure. Numbers in powers are also not counted as a significant number; hence there are only 2 significant digits in the last number. Therefore, option (A).