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

Multiple choice
  1. 24

  2. 47

  3. 49

  4. 48

Reveal answer Fill a bubble to check yourself
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.

Multiple choice
  1. 18

  2. 24

  3. 42

  4. 81

  5. None of these

Reveal answer Fill a bubble to check yourself
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.

Multiple choice
  1. 4

  2. 8

  3. 16

  4. 12

  5. None of these

Reveal answer Fill a bubble to check yourself
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.

Multiple choice
  1. 24

  2. 26

  3. 42

  4. 46

  5. None of these

Reveal answer Fill a bubble to check yourself
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

Multiple choice
  1. 69

  2. 78

  3. 43

  4. 76

  5. None of these

Reveal answer Fill a bubble to check yourself
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.