Unit Digit Questions for Competitive Exams

Finding the unit place of a number : unit digit questions in Hindi and English for Competitive Exams. Online practice test of selected questions from the previous year exam questions paper of SSC CGL, CHSL, GD and UPSSSC PET to help you achieve the highest possible score.

Number System Type 5: Unit Digit MCQ Test

Question 1:
The digit in unit’s place of the product 81 × 82 × 83 × … × 89 is
गुणनफल 81 × 82 × 83 × … × 89 के इकाई स्थान का अंक है
(1) 0
(2) 2
(3) 6
(4) 8

Show Answer and Solution
(1) 0
The digit in unit’s place = unit’s digit in the product 1 × 2 ×3 × …. × 9 = 0.

Question 2:
The digit in unit’s place of the product (2153)^{167} is :
गुणज के इकाई स्थान का अंक
(1) 1
(2) 3
(3) 7
(4) 9

Show Answer and Solution
(3) 7
Unit’s digit in 3^4 = 1
So, unit digit in 3^{164} = 1
Now, unit’s digit in
(2153)^{167}
= unit digit in 3^{167}
= unit digit in 3^{3} = 7

Question 3:
The digit in the unit’s place of the product
संख्याओं के गुणन के इकाई स्थान का अंक
2464^{615} . 131^{1793} . 317^{491} is
(1) 0
(2) 2
(3) 3
(4) 5

Show Answer and Solution
(1) 0
(4)^2m gives 6 at unit digit.
(4)^2m +1 gives 4 at unit digit.
(5)^n gives 5.
The same is the case with 1.
Required digit = Unit’s digit in the product of 4×5 × 1 = 0

Question 4:
In a two–digit number, the digit at the unit’s place is 1 less than twice the digit at the ten’s place. If the digits at unit’s and ten’s place are interchanged, the difference between the new and the original number is less than the original number by 20. The original number is
दो अंकों की संख्या में, इकाई के स्थान पर अंक दहाई के अंक के दोगुने से 1 कम है। यदि इकाई और दहाई के अंकों को आपस में बदल दिया जाए, तो नई और मूल संख्या के बीच का अंतर मूल संख्या से 20 कम है। मूल संख्या है
(1) 59
(2) 23
(3) 35
(4) 47

Show Answer and Solution

Ten’s digit = x
Unit’s digit = 2x – 1
Original number
= 10x + (2x – 1)
= 12x – 1
New number = 10 (2x – 1) + x
= 20x – 10 + x = 21x – 10
(21x – 10) – (12x + 1)
= 12x – 1 – 20
9x – 9 = 12x – 21
3x = 12
x = 4
Original number = 12x – 1
= 12 × 4 – 1 = 47

Question 5 :
There is a number consisting of two digits, the digit in the units’ place is twice that in the tens’ place and if 2 be subtracted from the sum of the digits, the difference is equal to \frac {1}{6} of the number. The number is
दो अंकों की एक संख्या है, इकाई के स्थान का अंक दहाई के स्थान के अंक का दोगुना है और यदि अंकों के योग में से 2 घटा दिया जाए, तो अंतर \frac {1}{6 } संख्या का । संख्या है
(1) 26
(2) 25
(3) 24
(4) 23

Show Answer and Solution
(3) 24
Ten’s digit of original number= x
Unit’s digit = 2x
Number = 10x + 2x = 12x
According to the question,
3x – 2 = \frac{1}{6} × 12x
3x – 2 = 2x
3x – 2x = 2
x = 2
Number = 12x = 12 × 2 = 2 = 24


Number System Questions for Competitive Exams – Online Study Test

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