Answer
B. 9.2
Step-by-step explanation
The square root can be approximated with the next formula:
[tex]\sqrt{x}\approx\frac{x+y}{2\sqrt{y}}[/tex]
where y is the nearest number to have an exact root.
In this case, we need to calculate the square root of x = 85. Using y = 81, we get:
[tex]\begin{gathered} x\approx\frac{85+81}{2\sqrt{81}} \\ x\approx\frac{166}{2\cdot9} \\ x\approx\frac{162+4}{18} \\ x\approx\frac{162}{18}+\frac{4}{18} \\ x\approx9+\frac{2}{9} \\ x\approx9+0.222... \\ x\approx9.2 \end{gathered}[/tex]
