Aptitude - Questions & Answers

Aptitude - Number System Online Quiz

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 - What is the unit digit in 7³⁵ - 3⁴⁸?

Answer : C

Explanation

Unit digit in 7³⁵ = (7⁴)⁸ x 7³
= 1 x 3 = 3
Unit digit in 3⁴⁸ = (3⁴)¹²
= 1
Therefore, unit digit in 7³⁵ - 3⁴⁸ = 3 - 1 = 2

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

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?

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 - The sum of all two digit numbers divisible by 7 is?

Answer : C

Explanation

7, 14, 21, ..., 98
A.P: a = 7, d = 7, l =98
t_n = 98
= a + (n - 1)d
i.e. 98 = 7 + (n - 1)7
n = 14
Sum = ⁿ⁄₂ (a + l)
= ¹⁴⁄₂ (7 + 98 )
= 735

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 - 5358 x 51 = y. What is y?

Answer : B

Explanation

  y =5358 x 51  =5358 x (50 + 1)  =5358 x 50 + 5358  =267900 + 5358  =273258

Q 8 - 106 x 106 + 94 x 94 = y. What is y?

Answer : B

Explanation

  y = 106 x 106 + 94 x 94    = (106)^{2^{+ (94)^{2^{= (100 + 6)^{2^{+ (100 -6)^{2^{Using formulae (a+b)^{2^{= a^{2^{+ b^{2^{+ 2ab and  (a-b)^{2^{= a^{2^{+ b^{2^{- 2ab  (a+b)^{2^{+ (a-b)^{2^{= 2(a^{2^{+ b^{2^{)  ∴ y = 2 x [(100)^{2^{+ (6)^{2^{]  = 2 x [10000 + 36]  = 2 x 10036  = 20072}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}

Q 9 - What is the first prime number?

Answer : C

Explanation

2 is the first prime number.

Q 10 - if a - b = 5 and a² + b² = 41, what is ab?

Answer : C

Explanation

  Using formulae (a-b)² = a² + b² - 2ab  ab = (a² + b² - (a-b)²) / 2  => ab = [41 - (5)²] / 2  = 8

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