Reasoning
Number Systems and Series
143 Questions
Number systems and series questions assess the ability to manipulate numerical values and spot patterns. The focus includes digit arrangements, binary conversions, and identifying largest or smallest numbers. These reasoning tasks are common across major competitive examinations.
Digit manipulationLargest and smallest numbersBinary number systemsPositional numeral systemsNumber series ranking
Number Systems and Series Questions
D
Correct answer
Explanation
This refers to Kaprekar's constant for 4-digit numbers. If you repeat the process of subtracting the smallest number from the largest number formed by the digits, you will always eventually reach 6174. The other numbers provided are not fixed points for this algorithm.
-
Power
-
Highest level of change
-
Everything
-
Thought
B
Correct answer
Explanation
In numerology, the digit 9 represents the highest level of change, completion, and culmination. It symbolizes the end of a cycle before a new one begins, and is associated with humanitarianism and universal love.
-
Comply Numbers
-
Faulty Numbers
-
Defective Numbers
-
None of the above
C
Correct answer
Explanation
In number theory, a deficient number (where the sum of proper divisors is less than the number) is also known as a defective number. 'Comply' and 'Faulty' are not standard mathematical terms for this classification.
A
Correct answer
Explanation
To answer this question, we need to understand that reading numbers backwards means that we read them from right to left. So, if we read the numbers 3-7-2-4-8-1-5 from right to left, we get 5-1-8-4-2-7-3. Therefore, the answer is A) True.
Correct Option: A
Explanation for the Correct Option:
The correct option is A because if we read the numbers 3-7-2-4-8-1-5 from right to left, we get 5-1-8-4-2-7-3. This is because reading numbers backwards means that we read them from right to left.
D
Correct answer
Explanation
To form a three-digit number with digits in ascending order from 1-9, we simply need to choose any 3 distinct digits - there's exactly one way to arrange them in ascending order. This is a combination problem: 9C3 = 9!/(3!×6!) = (9×8×7)/(3×2×1) = 84. The key insight is that choosing digits determines the arrangement uniquely.
C
Correct answer
Explanation
Let the 5-digit number be N. If we put 1 at the end, we get 10N + 1. If we put 1 at the beginning, we get 100000 + N. The condition says 100000 + N = 3(10N + 1), which simplifies to 100000 + N = 30N + 3, giving 99997 = 29N, so N = 42857.
-
Integers Number
-
Odd Number
-
Natural Number
-
Whole Number
A
Correct answer
Explanation
Integers are the set of whole numbers and their opposites, including negative numbers, zero, and positive numbers. Natural and whole numbers do not include negative values.
-
Odd Number
-
Even Number
-
Whole Number
-
Real Number
A
Correct answer
Explanation
Odd numbers are integers that cannot be divided evenly by 2, resulting in a remainder. The sequence 1, 3, 5, 7 follows this definition. Even numbers are divisible by 2, and whole numbers include zero.
-
Binary System
-
Barter System
-
Number System
-
Hexa Dexcimal System
A
Correct answer
Explanation
The Binary System uses only two digits: 0 and 1. This is the fundamental number system used in digital computing because electronic circuits can easily represent two states (on/off). Barter is an economic exchange system, not a number system.
D
Correct answer
Explanation
This is the triangular number sequence. The pattern shows the differences: 3-1=2, 6-3=3, 10-6=4, 15-10=5. Each difference increases by 1, so the next difference is 6, making the next number 15+6=21. Alternatively, these are 1, 1+2, 1+2+3, 1+2+3+4, 1+2+3+4+5.
-
Octal
-
Decimal
-
Hexadecimal
-
Binary
B
Correct answer
Explanation
The decimal number system (base 10) is what we use in everyday life, with digits 0-9. Octal is base 8, hexadecimal is base 16, and binary is base 2 - all used in computing but not in daily calculations.
C
Correct answer
Explanation
If the number is x, then 100000 + x is the number with 1 in front, and 10x + 1 is the number with 1 behind. The equation is 3(100000 + x) = 10x + 1. Solving gives 7x = 299999, so x = 42857.
-
1 and 4
-
4 and 5
-
2 and 4
-
2 and 3
-
1 and 5
D
Correct answer
Explanation
Counting frequency in: 2 3 4 2 1 3 4 2 8 7 5 2 1 3 4 6 2 3 4 1 9 5 3. 2 appears 5 times, 3 appears 5 times, 4 appears 4 times, 1 appears 3 times, 5 appears 2 times. Therefore, 2 and 3 have the maximum frequency (5 each), making Option D correct.
-
1113213211
-
1132123111
-
1331222211
-
1211121131
A
Correct answer
Explanation
This is the 'look-and-say' sequence: 1 is read as 'one 1' -> 11, 11 is 'two 1s' -> 21, 21 is 'one 2, one 1' -> 1211, etc. Continuing: 13112221 is 'one 1, one 3, two 1s, three 2s, one 1' -> 1113213211. The sequence describes the digits in the previous term.
C
Correct answer
Explanation
Let the 5-digit number be N. If we put 1 at the beginning, we get 100000 + N. If we put 1 at the end, we get 10N + 1. According to the problem: (10N + 1) = 3 × (100000 + N). Solving: 10N + 1 = 300000 + 3N → 7N = 299999 → N = 42857. Verification: 142857 ÷ 428571 = 1/3. The other options don't satisfy this mathematical relationship.