Question

How many significant digits are $50.00$ ?

Answer 1

The number of significant digits, $0 - 9$ are referred to as significant figures. These are written in a positional notation which carries the meaningful contribution of a digit in the measurement resolution. The numbers which belong to the significant figures within an expression of points to the confidence/conviction through which any engineer/ scientist asserts a quantity.

Complete step by step answer:
Significant figures rules:
1. Non-zero digits/numbers are known to be significant: In such cases, all non-zeros are considered as significant figures. i.e., $1 - 9$
Example, if you have $321.5$ then the significant figures are four i.e., $3,2,1{\text{ }}and{\text{ }}5$ are the significant figures.

2. Zeros appearing in-between the two non-zero or significant figures are significant: In this case, we can understand that all the zeros are counted if the zeros are in-between non-zeros.
Example, if you have $30201.05$ then the significant figures are seven i.e., $3,0,2,0,1,0{\text{ }}and{\text{ }}5$ are the significant figures.

3. Leading zeros (zeros appearing in-front of the significant figures are not significant: In this case, we can understand that all the zeros are not counted if the zeros are in-left side before non-zeros.
Example, if you have $00000.00215$ then the significant figures are three i.e., $2,1{\text{ }}and{\text{ }}5$ are the significant figures.

4. Trailing zeros (zeros appearing after the non-zero digits are significant figures): In this case, we can understand that all the zeros are counted if the zeros are an in-right side of digits having decimals.
Example, if you have $000030.00215$ then the significant figures are seven i.e., $3,0,0,0,2,1{\text{ }}and{\text{ }}5$ are the significant figures.
Suppose if we take $0.00092$ then the significant figures will be only two i.e., $9{\text{ }}and{\text{ }}2$.

So, in this $50.00$ we have four significant figures according to the trailing zeros. i.e., $5,0,0{\text{ }}and{\text{ }}0$.

Note: In a significant rule, there are three types of zeros, those are leading zero, captive zero and trailing zero. In leading zero, zeros are not counted as significant figures. In captive zero, the zeros are always counted. In trailing zeros, the zeros are counted when the non-zero having the decimal then is considered as a significant figure.