Question

solution of this question

Answer 1

(0.9)² - (0.1)²
0.81 - 0.01
0.8
answer will be (II) 0.8

Answer 2

Hey there!

Refer and consult the attachment for a detailed elaboration for normal values of squares of those numbers and a difference between the values to get the final answer that is,

$\boxed{\textbf{(ii) \: \: 0.8}}$

Hope this answer helps you and solves the doubts for squaring the values and finding numbers via subtraction!