Question

What will be the unit digit of the square of the number “1234”?
$
  {\text{A}}{\text{. 3}} \\
  {\text{B}}{\text{. 4}} \\
  {\text{C}}{\text{. 5}} \\
  {\text{D}}{\text{. 6}} \\
$

Answer 1

Hint – In order to find the unit digit of the square of the given number 1234, it is enough if we square the unit digit of 1234. Our answer is the unit digit of the obtained result.

Complete step-by-step answer:
Given data,
Number “1234”
The unit digit of the number 1234 is 4.
Now the square of the number 4 is given as,
$
   \Rightarrow {{\text{4}}^2} \\
   \Rightarrow 4 \times 4 \\
   \Rightarrow 16 \\
$
The unit digit of 16 is 6.
Hence the unit digit of the square of the number ‘1234’ is 6.
Option D is the correct answer.

Note – In order to solve this type of questions the key is to know that to find the units digit of the square of the number ‘1234’ it is enough to find the unit digit of the square of the unit digit of the given number, because irrespective of the other numbers the units digit is only dependent on unit digit place in any operation.
The same logic can be applied while adding, subtracting and multiplying a large number.
The square of a number ‘n’ is the product of n with itself, i.e. n×n.