Quantitative Aptitude
Number System and Digits
380 Questions
Number system and digits questions test the ability to manipulate numbers, identify significant digits, and form specific values. These problems often require finding missing digits or determining the properties of large sums. They form a vital component of the quantitative aptitude section.
Number formationMissing digitsSignificant digitsLargest and smallest numbersDigit sum properties
Number System and Digits Questions
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1023
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1024
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512
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none of the above
A
Correct answer
Explanation
With n binary digits, the range is 0 to 2^n - 1. For 10 bits: 2^10 - 1 = 1024 - 1 = 1023. This is the maximum unsigned value.
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224174
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425174
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6173
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225714
B
Correct answer
Explanation
Only option two gives 12A7C.
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(56)16
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(50)16
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(59)16
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None of these
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41620
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16204
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20164
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None of these
C
Correct answer
Explanation
20164 is the largest number formed by 4, 16, 20.
C
Correct answer
Explanation
The decimal number 16 in binary is 10000, which is 5 binary digits. This is calculated by repeatedly dividing by 2: 16 = 8 remainder 0, 8 = 4 remainder 0, 4 = 2 remainder 0, 2 = 1 remainder 0, 1 = 0 remainder 1, reading remainders backwards gives 10000.
B
Correct answer
Explanation
The decimal number 9 in binary is 1001, which has 4 binary digits. Converting: 9 = 4 remainder 1, 4 = 2 remainder 0, 2 = 1 remainder 0, 1 = 0 remainder 1, reading remainders backwards gives 1001.
D
Correct answer
Explanation
2^-48 equals 1 divided by 2^48, which requires 48 binary fraction digits to represent. In binary, this is 0.000...001 with 47 zeros followed by a 1 at the 48th position after the decimal point.
B
Correct answer
Explanation
In binary representation, the least significant bit determines parity. Odd numbers always have LSB=1 because they can be written as 2k+1, while even numbers have LSB=0 because they equal 2k.
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1023
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1024
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512
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None of these
A
Correct answer
Explanation
The number of numbers which can be represented by a 10-digit binary number will be 210 = 1024 and the numbers range from 0 - 1023. The maximum count which a 10-bit binary word can represent is 1023.
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18
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24
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42
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81
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None of these
B
Correct answer
Explanation
Let the ten's and unit digit be x and 8/x, respectively.
Then, (10x + 8/x) + 18 = 10 x (8/x) + x
10x2 + 8 + 18x = 80 + x2
9x2 + 18x - 72 = 0
x2 + 2x - 8 = 0
(x + 4)(x - 2) = 0
x = 2.
So, unit's digit = 4 and ten's digit = 2
Then, the required number is 24.
Therefore, the correct answer is 24.
B
Correct answer
Explanation
Since the number is greater than the number obtained on reversing the digits, so the ten's digit is greater than the unit's digit.
Let the ten's and the unit's digits be 2x and x, respectively.
Then, (10 x 2x + x) - (10x + 2x) = 36
9x = 36
x = 4
Required difference = (2x + x) - (2x - x) = 2x = 8
Therefore, 8 is the correct answer.
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145
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253
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370
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352
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None of these
B
Correct answer
Explanation
Let the middle digit be b.
Then, 2b = 10 or b = 5.
Let the number be abc.
Now, 100 a + 10 b + c + 99 = 100 c + 10 b + a
Or, a + 1 = c
So, the number is 253
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24
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26
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42
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46
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None of these
A
Correct answer
Explanation
Let the ten's digit be x.
Then, unit's digit will be x + 2.
The number = 10x + (x + 2) = 11x + 2
The sum of digits = x + (x + 2) = 2x + 2
(11x + 2)(2x + 2) = 144
22x2 + 26x - 140 = 0
11x2 + 13x - 70 = 0
(x - 2)(11x + 35) = 0
x = 2
Hence, the required number = 11x + 2 = 24
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69
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78
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43
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76
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None of these
A
Correct answer
Explanation
Let the ten's digit be x and unit's digit be y.
Then, x + y = 15 and x - y = 3 or y - x = 3.
Solving x + y = 15 and x - y = 3,
we get: x = 9, y = 6.
Solving x + y = 15 and y - x = 3,
we get: x = 6, y = 9.
So, the number is either 96 or 69.
Hence, out of the given options, option (1) is correct.
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3
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4
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9
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Cannot be determined
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None of these
B
Correct answer
Explanation
Let the ten's digit be x and the unit's digit be y.
Then, (10x + y) - (10y + x) = 36
9(x - y) = 36
x - y = 4