How To Solve Number System Questions Quickly

August 29, 2019

How to Solve Quickly Number System Questions

Number system is a technique to represent number and present number in discrete manner.

Whole Number, Rational Number, Natural Number, Odd Number, Even Number, Irrational Number etc are general type of Number System.

Type 1: How To Solve Number System Question Quickly.

Question 1.

34567 * 9999 =?
Options.
A. 345635432
B. 345634533
C. 345635433
D. 345635343

Solution:

34567 * 9999 = 34567 * (10000 – 1)
34567 * 9999 = 34567 * (10000) – 34567 * 1
34567 * 9999 = 345670000 – 34567
34567 * 9999 = 345635433

Correct option: C

Question 2.

The smallest 3 digit prime number is:
Options
A. 100
B. 103
C. 105
D. 101

Solution:

The smallest three digit number is 100 but it is not a prime number. The next number is 101 and it is a prime number. Therefore, 101 is the smallest 3 digit prime number.

Correct option: D

Question 3.

Choose the terminating decimal

Options

A. 99.5555
B. 3.777
C. 0.6
D. 0.454545454545

Solution:

A terminating decimal is a decimal that ends after few repetitions after decimal point.
Correct option: C

Question 4.

Which of the following is not the Natural number?

Options
A. 1
B. 3
C. 0
D. 5

Solution:

All counting numbers from 1 to infinity are natural numbers.

Correct option: C

Question 5.

Choose the non- terminating decimal?
Options
A. 4/45
B. 5/8
C. 1/4
D. 9/1280

Solution:

4/45 = 0.08888…
5/8 = 0.625
1/4 = 0.25
9/1280 = 0.00703125

Correct option: A

how to Solve Questions on Number System Quickly

Question 6

6596 – ? = 6459 – 3357
Options
A. 3949
B. 3494
C. 3102
D. 3499

Solution:

6596 – x = 3102
-x = 3102 – 6596
– x = – 3494
x = 3494

Correct option: B

Question 7

Which one of the following cannot be the square of natural number?
Options
A. 7225
B. 3136
C. 8100
D. 3457

Solution:

7885 = (85)²
3136 = (56)²
8100 = (90)²
3457 is not the square of any natural number as square of any natural number never ends with 7.

Correct option: D

Question 8

What is the unit digit in the product (3⁶⁵ * 6⁵⁹ * 7⁷¹)?
Options
A. 1
B. 2
C. 3
D. 4

Solution:

Unit digit in 3⁴ = 1
So, Unit digit in (3⁴)¹⁶ = 1
Unit digit in 365 = 3⁶⁵ = (3⁴)¹⁶ x 3¹ = (1 * 3) = 3
Unit digit in 6⁵⁹ = 6
Unit digit in 7⁴ = 1

So, Unit digit in(7⁴)¹⁷ is 1
Unit digit in 7⁷¹ = (7⁴)¹⁷ x 7³ = (1 * 3) = 3
Required digit = Unit digit in (3 * 6 * 3) = 4

Correct option: D

Question 9

117 * 117 + 83 * 83 = ?

Options

A. 40578
B. 20578
C. 31090
D. 34567

Solution:

(117)² + (83)² = (100 + 17)² + (100 – 17)²
= 2 * (100)² + (17)²
= 2 * 10000 + 289
= 2 * 10289
= 20578

Correct option: B

Question 10.

The unit digit in the product (842 * 618 * 234 * 567) is:
Options
A. 4
B. 3
C. 8
D. 6

Solution:

Unit digit in the given product = Unit digit in (2 * 8 * 4 * 7) = (448) = 8

Correct option: C

Read Also – Formulas to solve number system questions

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