Question

Find the unit place value of a square of a number who has 6 in its unit place.
A. 18
B. 6
C. 9
D. 4

Answer 1

Hint: We find out how the unit place is created in a square number. We find out the responsible numbers to form the unit place. Then we take the multiplication of those numbers to find out possible numbers that can appear in the unit place of the square.

Complete step-by-step answer:
Here it’s given that a number has 6 in its unit place. We are going to take the square of that number. We need to find the unit place value of that square.
When two numbers are multiplied any place value of that multiplied number is created by the multiplication of same place values of those numbers being multiplied and the addition of the carried over numbers from previous placed values.
For unit place values there are no values to be carried over as the multiplication starts from the unit place. So, the numbers responsible for unit place value are only the multiplication of the unit place values.
We are multiplying two numbers who have 6 in their unit place. Both have 6 as the same number gets multiplied in square.
So, the multiplication of two 6’s gives $6\times 6=36$.
We got a unit placed 6 out of 36 and then the 3 of that part gets carried over to the tenth-place value.
So, in the unit place only 6 remains.
For example, let’s take 76. It has 6 in its unit place.
We take squares of 76 which is $76\times 76$.
So, $76\times 76=5776$. It also has 6 in its unit place.
The unit place value of a square of a number who has 6 in its unit place will be also 6.

So, the correct answer is “Option B”.

Note: We need to remember the implication of the carried over values. In the unit place cases we don’t need to care about that but in other cases we need to find out the carried over values.