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.