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.