Rules For Finding Significant Figures With
Examples
While finding significant digits, we have to
determine important digits that convey the meaning of the given numbers based
on accuracy. To find these figures, we have to keep in mind some rules.
1.
All Non-Zero Digits are Significant Figures
The digits other than zero are non-zero
digits. For example, 1, 2, 3, 4, etc. are non-zero digits. For example, if we
have a reading of 6745, it contains 4 non-zero digits. It means that it has 4
significant figures.
2.
Zeroes Between Non-Zero Digits Are Also Significant Figures
If we are taking a reading, we can get zeroes.
For example, we can get readings as 1008, 20187, 789001, etc. These readings
show that these zeroes are in between non-zero digits. According to the rules
for finding significant figures, these zeroes are also significant. In the
readings 1008, 20187, and 789001, there are 4, 5, and 6 significant figures
respectively.
3.
Rules For Zeroes on Right and Left Side of Non-Zero Digits
For example, we have two reading 00756 and
89400. In the first reading 00756, we have two zeroes on the left side of the non-zero
digits. These zeroes are non-significant digits. Therefore, we have only 3
significant figures in this reading. On the other hand, in reading 89400, we
have zeroes on the right side of the non-zero digits. According to the rules
for finding significant figures, these zeroes are significant. Therefore, this
reading has 5 significant figures.
If we want to understand this concept more
accurately, we have to see the last non-zero digit from the right and left
sides. In the reading 00756, 7 is the last non-zero digit from the left side.
All the zeroes after this non-zero digit are non-significant. Similarly, we
should also see the last non-zero digit from the right side. In reading 89400,
4 is the last non-zero digit from the right side. All the zeroes after this
non-zero digit are significant.
4.
Rules For Zeroes on Right and Left Side of Decimal Points
To understand this rule for finding
significant figures, we also take two examples. These examples are 000.678 and
78.000. In the first example 000.678, we have three zeroes on the left side of
the decimal point. According to the rules for finding significant figures,
these zeroes are non-significant. Therefore, there are only 3 in this example.
On the other hand, in the example 78.000, we have three zeroes on the right
side of the decimal point. These zeroes are significant. Therefore, there are 5
significant figures in this example.
Rounding Off Significant Figures
To get more precise results, we may have to
round off these figures. For this reason, we have to keep in mind some
important things.
·
First
of all, we have to know up to which digit we want to round off the given number.
For example, we have a number 67.546712 and we want to round off this number up
to two digits after the decimal point. It means that we have to skip 6712 from
this number.
·
Secondly,
we have to see the digit just after the digit that we want to round off. In
this example 67.546712, we have to see the digit after 4 and this digit is 6.
·
If
this digit is less than 5, we can round off this digit without making any
change. For example, if we have a number 89.45341 and we want to round off this
number up to two decimal places, we will get 89.45. Its reason is that after
the second digit, we have 3 and it is less than 5. That’s why we can skip the
digits after two decimal places without making any change.
·
If
this digit is 5 or greater than 5, we have to add 1 in the last digit. In the
previous example 67.546712, we have 6 after two decimal places. It is greater
than 5. Therefore, we have to add 1 to the number and our answer will be 67.55.
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