find the last two digits of 181^58
Answers
The objective of this article is to understand the concept and approach to solve questions like:
Find the last two digits of
2
234
31
123
73
35
There are two-three shortcut approaches to solve the above problems. But before we go and apply the same, we need to understand the following basic points.
Finding the last two digits of a square of any number:
Let’s take an example; say we need to find the last two digits of
78
2
. The prerequisite is to memorise the square of the first 25 natural numbers.
Now, number 78 is close to 100 and the deviation of 78 from 100 is 22 (100-78). So we can write
78
2
=
(
100
–
22
)
2
=
100
2
–
2
×
100
×
22
+
22
2
=
10000
–
4400
+
484
Now observe that the last two digits of the first two terms are 00, 00, and 84.
So the last two digits of
78
2
≡
last two digits of
(
100
–
22
)
2
≡
last two digits of
22
2
Similarly, the last two digits of
61
2
≡
(
50
+
11
)
2
≡
11
2
≡
21
From the above examples, we can deduce that the if the number is close to 100 or 50, the last two digits of the square of the number is equal to the last two digits of the square of the deviation of the number from the base 100 or 50 (whichever the number if close to).