89^2= ____ A. (90-1)^2 B. 90^2 C. 1^2 D. 9^2 The question was

89-2-a-90-1-2-b-90-2-c-1-2-d-9-2-the-question-was

89^2= ____

A. (90-1)^2

B. 90^2

C. 1^2

D. 9^2

The question was posed to me in an international level competition.

My question is based upon Finding the Square of a Number in chapter Squares and Square Roots of Mathematics – Class 8

The correct option is A. (90-1)^2

For explanation I would say: If we have to find the square of the number which is near 0 we use the second variation i.e. (90-1)^2. This would help us and make the calculations easier.

Therefore (90-1)^2= 90^2-2×90×1+1^2

Therefore (90-1)^2= 8100-180+1

Therefore (90-1)^2=7921.