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Aptitude - Number System Online Quiz

Following quiz provides Multiple Choice Questions (MCQs) related to Number System. You will have to read all the given answers and click over the correct answer. If you are not sure about the answer then you can check the answer using Show Answer button. You can use Next Quiz button to check new set of questions in the quiz.

Q 1 - The unit digit in the product (536 x 764 x 358)?

Answer : C

Explanation

Unit Digit = Unit Digit in (6 x 4 x 8)
= 2

Q 2 - The sum of even numbers between 1 and 21 is?

Answer : A

Explanation

A.P -> a = 2, l = 20
-> a + (n - 1)d = 20
-> 2 + (n - 1) x 2 = 20
-> n = 10 i.e. terms = 10
S₂ = ⁿ⁄₂ (a + l)
= ¹⁰⁄₂ x (2 + 20)
= 110

Q 3 - Which of the following is a prime number?

Answer : D

Explanation

151 is greater than 12
All prime numbers less than 12 is 2, 3, 5, 7, 11
24 is divisible by 3 i.e. not prime
35 is divisible by 5 i.e. not prime
125 is divisible by 5 i.e. not prime
151 is divisible by 2, 3, 5, 7, 11 i.e. prime number.

Q 4 - When a number is divided by 17, the remainder is 9. When the same number is divided by 23, the remainder is 4. Find the number?

Answer : B

Explanation

x = 17p + 9 and x = 23q + 4
i.e. 17p + 9 = 23q + 4
Therefore, q = (17p + 5)/23
Least value of p for which q is a whole number is p = 20
x = 17p + 9
= 17 x 20 + 9
= 349

Q 5 - The largest three digit multiple of 32?

Answer : B

Explanation

999 is the largest three digit number.
On dividing 999 by 32, remainder is 7.
999 - 7 = 992
Therefore, 992 is the largest three digit multiple of 32.

Q 6 - 1² - 2² + 3² - 4² +..+ 9² -10²?

Answer : D

Explanation

   Using formula a² - b² = (a-b)(a+b) 1² - 2² + 3² - 4² +..+ 9² -10² = (1-2)(1+2) + (3-4)(3+4) + (5-6)(5+6) + (7-8)(7+8) + (9-10)(9+10) = (-3) + (-7) + (-11) + (-11) + (-15) + (-19) = -55

Q 7 - (45 + 46 + 47 + ... + 114 + 115) = ?

Answer : C

Explanation

  Using formula for sum of natural numbers  (1 + 2 + 3 +... + n) = (1/2)n(n+1)  (45 + 46 + 47 + ... + 114 + 115) = (1 + 2 + 3 +... + 115) - (1 + 2 + 3 + ... + 44)  = (1/2) x 115 x 116 - (1/2) x 44 x 45  = 115 x 58 - 22 x 45  = 6670 - 990  = 5680

Q 8 - 1506 x 1506 = y. What is y?

Answer : D

Explanation

  y = 1506 x 1506   = (1500 + 6) x (1500 + 6)  = (1500 + 6)^{2^{Using formulae (a+b)^{2^{= a^{2^{+ b^{2^{+ 2ab  ∴ y = (1500)^{2^{+ (6)^{2^{+ 2 x 1500 x 6  = 2250000 + 36 + 18000  = 2268036}}}}}}}}}}}}

Q 9 - a,b,c and d are consecutive odd number with average 42. What is the product of b and d?

Answer : C

Explanation

  let a = 2n + 1, b = 2n + 3, c = 2n + 5 and d = 2n + 7  Now (a + b + c + d) / 4 = 42  => (2n + 1 + 2n + 3 + 2n + 5 + 2n + 7) = 42 x 4  => 8n + 16 = 168  => n  = 152 / 8  => n = 19  ∴ b x d = (2 x 19 + 3) x (2 x 19 + 7)  = 41 x 45  = 1845

Q 10 - if the sum of three consecutive odd numbers is 3 more than twice of the third. What is the largest number?

Answer : C

Explanation

  Let's the numbers be a, a + 2, a + 4  => (a + a + 2 + a + 4) =  [2 x (a + 4)] + 3  => 3a + 6 = 2a + 11  => a = 5   => largest number is 9