Nolan is finding estimated square root, his every steps are absolutely correct and he did not make any error.
Nolan want to find estimate value of [tex]\sqrt{18}[/tex]
Since, [tex]4^{2}=16, 5^{2} =25[/tex] and 16 < 18 < 25
So that, [tex]\sqrt{18}[/tex] lies between 4 and 5.
Since 18 is closer to 16, square the tenths closer to 4.
[tex](4.1)^{2} = 16.81\\\\(4.2) ^{2} = 17.64\\\\(4.3) ^{2} = 18.49\\\\(4.4) ^{2} = 19.36[/tex]
after observing above , 18.49 is rounds to 18.
Hence, 4.3 is the best approximation for [tex]\sqrt{18}[/tex]
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