Aptitude - Number System Online Quiz


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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.

Questions and Answers

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

A - 4

B - 3

C - 2

D - 1

Answer : C

Explanation

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

Q 2 - If the number 517 * 324 is completely divisible by 3, then the smallest whole number in place of * will be?

A - 0

B - 3

C - 1

D - 2

Answer : D

Explanation

For this:
= (5 + 1 + 7 + x + 3 + 2 +4)
= 22 + x
Now, 22 + x must be divisible by 3. So, for this x should be 2.
22 + 2 = 24 i.e. divisible by 3

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

A - 24

B - 35

C - 125

D - 151

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 - If p is a natural number, then (6p2 + 6p) is always divisible by?

A - 12 only

B - both 6 and 12

C - 15 only

D - 18 only

Answer : B

Explanation

(6p2 + 6p)
= 6p (p + 1)
p(p+1) is always even, so it will always be divisible by 6 and 12.

Q 5 - How many three digit numbers are completely divisible by 6?

A - 95

B - 135

C - 110

D - 150

Answer : D

Explanation

102, 108, 114...996 are three digit numbers divisible by 6
It can be seen that its an A.P with a= 102, d = 6 and l = 996
Let number of terms be n, therefore tn = 996
996 = a + (n - 1)d
996 = 102 + (n - 1) x 6
n = 150 -> number of terms

Q 6 - 12 - 22 + 32 - 42 +..+ 92 -102?

A - 45

B - -45

C - -54

D - -55

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 - (112 + 122 + 132 + ... + 202) = ?

A - 385

B - 2485

C - 2870

D - 3235

Answer : B

Explanation

  Using formula for sum of squares of natural numbers  (12 + 22 + 32 +... + n2) = (1/6)n(n+1)(2n+1)  (112 + 122 + 132 + ... + 202) = (12 + 22 ... + 202) - (12 + 22 ... + 102)  = (1/6) x 20 x 21 x 41 - (1/6) x 10 x 11 x 21  = 2870 - 385  = 2485  

Q 8 - 217 x 217 + 183 x 183 = y. What is y?

A - 79698

B - 80578

C - 80698

D - 81238

Answer : B

Explanation

  y = 217 x 217 + 183 x 183    = (217)2 + (183)2  = (200 + 17)2 + (200 -17)2  Using formulae (a+b)2 = a2 + b2 + 2ab and  (a-b)2 = a2 + b2 - 2ab  (a+b)2 + (a-b)2 = 2(a2 + b2)  ∴ y = 2 x [(200)2 + (17)2]  = 2 x [40000 + 289]  = 2 x 40289  = 80578  

Q 9 - What is the largest number which can divide n3 - n for every natural number n?

A - 2

B - 3

C - 6

D - 12

Answer : A

Explanation

  (2)3 - 2 = 6   ∴ 6 is the largest number which can divide n3 - n for every natural number n.  

Q 10 - The product of two numbers is 9375 and quotient is 15. What is the sum of the numbers?

A - 350

B - 400

C - 450

D - 500

Answer : B

Explanation

  Let's have numbers as a and b  Thus ab = 9375 and a/b = 15  => ab / (a/b) = 9375 / 15  => (b)2 = 625  => b = 25  => a = 15b = 15 x 25 = 375  ∴ a + b = 375 + 25 = 400  



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