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 - 20 + 15 X 3.5 = ?

A - 72

B - 72.5

C - 62.5

D - none of these

Answer : B

Explanation

= 20 + 15 x 3.5
= 20 + 15 x (7/2)
= 20 + 52.5
= 72.5

Q 2 - Which of the numbers is exactly divisible by 3?

A - 415591

B - 6472

C - 3364

D - 413976

Answer : D

Explanation

Divisibility by 3: if sum of the digits is divisible by 3 then original number is divisible by 3. 413976, sum of digits is 30 thus the number is divisible by 3.

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

A - 7

B - 9

C - 12

D - 20

Answer : A

Explanation

7 as it has no positive divisors except 1.

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 - 6 + 15 + 24 + 33 + ... + 123 = ?

A - 903

B - 603

C - 752

D - 690

Answer : A

Explanation

a = 6, d = 9, l = 123
Let number of terms be n
123 = a + (n - 1)d
123 = 6 + (n - 1)9
123 = 9n - 9
n = 14
Sn = n2 (a + l)
= 142 (6 + 123)
= 7 x 129
= 903

Q 6 - What is the unit digit in in 365 x 659 x 771 ?

A - 1

B - 2

C - 4

D - 6

Answer : C

Explanation

  365 = (34)6 x 3 So Unit digit in 365 = Unit digit in 1 x 3 = 3  659 = (64)14 x 63 So Unit digit in 659 = Unit digit in 6 x 216 = 6  771 = (74)17 x 73 So Unit digit in 771 = Unit digit in 1 x 343 = 3  So Unit digit in 365 x 659 x 771 = Unit digit in 3 x 6 x 3 = 4.

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

A - 5600

B - 5656

C - 5680

D - 5000

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 - 106 x 106 - 94 x 94 = y. What is y?

A - 2400

B - 2000

C - 1904

D - 1906

Answer : A

Explanation

  y = 106 x 106 - 94 x 94     = (106)2 - (94)2   = (100 + 6)2 - (100 - 6)2   Using formulae (a+b)2 = a2 + b2 + 2ab  and  (a-b)2 = a2 + b2 - 2ab   (a+b)2 - (a-b)2 = 4ab   ∴ y = 4 x 100 x 6  = 2400  

Q 9 - Which of the following is a prime number?

A - 81

B - 33

C - 93

D - 97

Answer : D

Explanation

97. As all other numbers are divisible by 3.

Q 10 - How many numbers are divisible by all 4,5 and 6 lying between 200 and 600.

A - 5

B - 6

C - 7

D - 8

Answer : B

Explanation

Each number should be divisible by L.C.M. of 4, 5 and 6 i.e. 60. So numbers are 240, 300, 360, 420, 480, 540. Count: 6



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