In example 2 10 Physics part 1 ncert chapter 2 , IN NCERT IT IS WRITTEN THAT DELTA R IS - Physics - Units And Measurements

Question

In example 2 10 Physics part 1 ncert chapter 2 , IN NCERT IT IS
WRITTEN THAT DELTA R IS EXPRESSED AS 1 8 INSTEAD OF 2 BECAUSE OF
THE RULES OF SIGNIFICANT FIGURES
SO I WOULD LIKE EXPERTS TO TELL ME WHICH RULE IS IT TALKING ABOUT
AND WHY HAVE WE ACTUALLTY TAKEN 1 8 AND NOT 2 WHICH NUMBER'S
SIGNIFICANT FIGURES IS IT TALKING ABOUT I WANT THE PROPER ANSWER TO
MY QUESTION

Ved Prakash Lakhera · Accepted Answer

When we find R'=66
7ohm then there is accuracyupto one digit after decimal point
So when finding ∆R', we should have should have same precision and accuracy upto one digit after decimal point
Therefore the value of ∆R'=1
8, not 2
It means the place up to one digit soon after decimalpoint is significant not round off value 2