Question

Estimate the square root of 320 to the nearest whole number.

• A. 20
• B. 32
• C. 19
• D. 18

Answer 1

The correct option is D 18

320 lies between the common perfect squares, namely, 225 and 400.
225 < 320 < 400, Taking square root, $\sqrt{225}$ < $\sqrt{320}$< $\sqrt{400}$
= 15 < $\sqrt{320}$ < 20
15 and 20 are not consecutive numbers. Hence, we need to narrow down our search, till we obtain two consecutive perfect squares between which 320 lies.
We know that ${17}^2$ = 289 and ${18}^2$ = 324.
The number 320 lies between 289 and 324. and is closer to 324. ( $\sqrt{324}$ = 18)
Hence, the esimated square root of 320 to the nearest whole number will be =18