Quantitative Aptitude

Number System and Digits

374 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 cobol

using an ____number of digits for PACKED DECIMAL (COMP-3) is 5% to 20% Faster than using an_____ number of digits .

  1. Even, Even

  2. Odd, Even

  3. Odd, Odd

  4. Even, Odd
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In COBOL, PACKED DECIMAL (COMP-3) format performs faster with an odd number of digits because of how the packed decimal format stores digits (2 digits per byte plus sign nibble). Even digit counts require padding which impacts performance by 5-20%.

Multiple choice general knowledge math & puzzles

The digit in the unit's place of a number is equal to the digit in the ten's place of half of that number and the digit in the ten's place of that number is less than the digit in the unit's place of half of that number by 1. If the sum of the digits of the number is 7, then what is the number?

  1. 34

  2. 52

  3. 162

  4. data inadequate
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let the number be 10a + b where a is tens digit and b is units digit. Half of 52 is 26. The units digit of 52 (which is 2) equals the tens digit of 26 (which is 2). Also, the tens digit of 52 (which is 5) equals the units digit of 26 (which is 6) minus 1. The sum of digits 5 + 2 = 7. All conditions are satisfied.

Multiple choice general knowledge math & puzzles

The square of a two digit number is divided by half the number. After 36 is added to the quotient, this sum is then divided by 2. The digits of the resulting number are the same as those in the original number, but they are in reverse order. The ten's place of the original number is equal to twice the difference between its digits. What is the number?

  1. 45

  2. 36

  3. 46

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the number be 10A + B. Following the operations: square it, divide by half (=multiply by 2), add 36, divide by 2. This gives 10A + B + 18, which equals the reverse 10B + A. Solving: A - B = -2, so B = A + 2. Given A = 2(B - A), we get 3A = 2B, substituting: 3A = 2(A + 2), giving A = 4, B = 6. The number is 46, and 46² ÷ 23 + 36 all divided by 2 = 64.

Multiple choice general knowledge math & puzzles

Number y is defined as the sum of the digit of the number x, and z as the sum of the digits of the number y. How many natural numbers x satisfy the equation x+y+z = 60?

  1. 1

  2. 2

  3. 3

  4. 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let x be the original number, y be the sum of its digits, and z be the sum of digits of y. We need x + y + z = 60. The maximum possible sum of digits for any number grows slowly. Testing valid natural numbers: x=48 gives y=12, z=3, so 48+12+3=63. x=47 gives y=11, z=2, so 47+11+2=60 (valid). x=38 gives y=11, z=2, so 38+11+2=51. x=29 gives y=11, z=2, so 29+11+2=42. x=19 gives y=10, z=1, so 19+10+1=30. Continuing this systematic search, we find exactly 3 solutions exist.

Multiple choice general knowledge math & puzzles

The digit in the units place of a two-digit number exceeds that in the tens place by one. If the number is equal to four times the sum of its digits, find that number!

  1. 12

  2. 14

  3. 16

  4. 18
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the tens digit be x and the units digit be y. We know y = x + 1, and the number is 10x + y = 4(x + y). Substituting: 10x + (x + 1) = 4(x + x + 1), which simplifies to 11x + 1 = 8x + 4, giving 3x = 3, so x = 2. Then y = 3, making the number 23. Wait, that doesn't match option A (12). Let me re-check. If the number is 12: digits are 1 and 2. Units (2) exceeds tens (1) by 1. Sum of digits = 3. Four times sum = 12. This matches.

Multiple choice general knowledge math & puzzles

What is the maximum natural number that can be formed using only two 2's??

  1. 32

  2. 22

  3. 22!

  4. 20
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

22! (22 factorial) = 22 × 21 × 20 × ... × 1 is an extremely large number that far exceeds 22, 32, or 20. Factorials grow faster than exponential functions, so 22! is the maximum possible number that can be formed using exactly two 2's with mathematical notation. 22! is approximately 1.124 × 10^21.

Multiple choice general knowledge math & puzzles

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

  1. 5/9

  2. 5-9

  3. 5.9

  4. 5*9
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A decimal point between 5 and 9 makes 5.9, which is greater than 5 and less than 9. Division (5/9 ≈ 0.556) gives a smaller number. Subtraction (5-9 = -4) is negative. Multiplication (5*9 = 45) is too large. Only the decimal point satisfies the condition.

Multiple choice general knowledge math & puzzles

I am thinking of a 6-digit number. The sum of the digits is 43. And only two of the following three statements about the number are true: (1) it's a square number, (2) it's a cube number, and (3) the number is under 500000.

  1. 499849

  2. 567342

  3. 111111

  4. 333333
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

499849: Sum of digits = 4+9+9+8+4+9 = 43 ✓. It's a square number (707²) ✓, but not a cube (cube root ≈ 79.3) ✗. It's under 500,000 ✓. So exactly two statements are true (1 and 3), satisfying the condition. Other options fail various checks.