Answer:
• All non-zero digits in a number are significant.
Example: Numbers 0.0000216, 0.0216, 21.6 and 216 have the same number of significant figures namely three (2, 1, 6).
• All zeros between two non-zero digits are significant, no matter where the decimal point is, if at all.
Example : In the numbers 0.0000206, 0.0206, 20.6 and 206, the zero lying between the digits 2 and 6 is only significant.
• If the number is less than 1, the zeroes on the right of decimal point but to the left of the first non-zero digit are not significant.
Example : In 0.0000206, the four zeros after decimal and before the digit 2 has no significance. Similarly, in 0.0206, the zero after decimal and before the digit 2 has no significance. So the number of significant figures of these numbers are three (2, 0 and 6).
Hope this helps, have a nice day/night! :D