IBPS Sample Problems On Unit Digit

Below are four problems on unit digit, you have to find the unit digit of a product or sum or power of the numbers.

Question 1

The unit digit of the sum 1289 + 2541 + 8215 + 6137 is:
a) 1 b) 2 c) 9 d) 3

Solution:

The required answer is the unit digit of the sum of the unit digits of the numbers in given sum.
i.e., The unit digit of (1289 + 2541 + 8215 + 6137)
= the unit digit of (9+1+5+7)
= the unit digit of (22)
= 2

Question 2

The unit digit of the product 1022 x 729 x 889 x 971 is:
a) 2 b) 9 c) 1 d) 8

Solution:

The required answer is the unit digit of the product of the unit digits of the numbers in given product.
i.e, The unit digit of (1022 x 729 x 889 x 971)
= the unit digit of (2 x 9 x 9 x 1)
= the unit digit of (162)
= 2

Question 3

Find the unit digit of (7493263)x(15129)
a) 3 b) 9 c) 7 d) 1

Solution:
The given product is (7493263)x(15129)
Required unit digit = the unit digit of(3263)x(129) ...(1)
In the value of 3 to the power 4, we have the unit digit as 1.
so, we can rewrite (3263) = [3(4x65 + 3)] = [(34)65] x (33)
Then from eqn(1),
The unit digit of(3263)x(129) = The unit digit of[(34)65] x (33) x 129
= The unit digit of[165] x 27 x 1
= The unit digit of 1 x 7 x 1 = 7

Question 4

Find the unit digit of 634262 + 634263
a) 0 b) 1 c) 4 d) 6

Solution:

Given that 634262 + 634263
= 634262(1 + 634)
= (634262) x 635
The unit digit of (634262) x 635 = the unit digit of (4262 x 5)
We know that, the unit digit of 4 to the power of any odd number is 4 and the unit digit of 4 to the power of any even number is 6.
Then the unit digit of (4262 x 5) = unit digit of(6 x 5) = 0

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