Aptitude - Arithmetic Online Quiz


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Following quiz provides Multiple Choice Questions (MCQs) related to Basic Arithmetic. 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 - What is the 105th term of A.P. 4, 4.5, 5, 5.5 ... ?

A - 56

B - 55.5

C - 56.5

D - 55

Answer : A

Explanation

Here a = 4, d = 4.5 - 4 = 0.5, n = 105 
Using formula Tn = a + (n - 1)d 
T105 = 4 + (105 - 1) x 0.5 
= 56 

Q 2 - What digit should be placed in of H in 78423928H9 so as make it divisible by 9?

A - 3

B - 4

C - 7

D - 2

Answer : D

Explanation

  
For the number 78423928H9 to be divisible by 9, the sum of all  its digits should be divisible by 9.  
So                        (7+8+4+2+3+9+2+8+2+9)/9 = (52+H)/9 
= Number divisible by 9  
So H should b replaced by 2  

Q 3 - The sum of first 99 natural numbers is?

A - 9801

B - 9800

C - 4851

D - 4950

Answer : D

Explanation

  
 Sum of n natural numbers is  Sn=n(n+1)/2  =99(99+1)/2  
 =4950  

Q 4 - If (28)3 is subtracted from the square of a number, the answer so obtained is 1457. What is the number?

A - 127

B - 136

C - 142

D - 153

Answer : D

Explanation

 
 Let the number = x 
 According to question, x2 - 283 = 1457 
 or, 
 x = 153 

Q 5 - If 10th term of A.P. a, a-b, a-2b, ... is 20 and 20th term is 10 then what will be xth term?

A - 10-x

B - 20-x

C - 29-x

D - 30-x

Answer : D

Explanation

  
 Here a = a-b,  d = (a-2b) - (a-b) = -b,    
 Using formula Tn = a + (n - 1)d    
 T10 = (a-b) + (10 - 1) x (-b) = 20    
 => a - 9b = 20 ... (i) 
 T20 = (a-b) + (20 - 1) x (-b) = 10    
 => a - 19b = 10 ... (ii) 
 Subtracting (ii) from (i) 10b = 10 
 => b = 1 
 Using (i) a - 9(1) = 20 
 => a = 29 
 ∴ xth term = a + (x-1)d 
 = a + (x-1)(-b) = 20 + (x-1)(-1) 
 = 30-x 

Q 6 - if a, a-2 and 3a are in an A.P. what is a?

A - -3

B - -2

C - 2

D - 3

Answer : B

Explanation

 
 As a, a-2 and 3a are in an A.P. 
 ∴ (a-2) - a = 3a - (a-2) 
 => -2 = 2a - 2 
 => a = -2 

Q 7 - What is the sum of (1 + 1/2 + 1/4 + ...)?

A - 2

B - 4

C - 8

D - 10

Answer : A

Explanation

  
 This is an infinite G.P. with a = 1 and r = 1/2.  
 Sum of infinite G.P. = a/(1-r)  = 1/(1-1/2)  = 1/(1/2)  = 2 

Q 8 - 142 + 152 ... + 302 = ?

A - 3836

B - 8336

C - 8366

D - 8636

Answer : D

Explanation

  
 Using formula  (12 + 32 ... +  n2) = [n(n+1)(2n+1)]/6  
 142 + 152 ... + 302 = (12 + 22 ... + 302) - (12 + 22 ... + 132)  
 = (30 x 31 x 61)/ 6 - (13 x 14 x 27) / 6  
 = 9455 - 819  = 8636 

Q 9 - If 12 + 22 ... + 102 = 385. What is 22 + 42 +... + 202?

A - 770

B - 1155

C - 1540

D - 3852

Answer : C

Explanation

   
 (22 + 42 ... + 202)  = (1 x 22 + 22 x 22 + 32 x 22 +... +  102 x 22)  
 = 22(12 + 22 + .... + 102) 
 = 4 x  385  
 = 1540 

Q 10 - How many 2 digits numbers are there which are divisible by 6?

A - 12

B - 15

C - 16

D - 17

Answer : B

Explanation

  
 Here series is 12, 18, 24, ... 96.  
 Here a = 12,  d = 18 - 12 = 6     
 Using formula Tn = a + (n - 1)d     
 Tn = 12 + (n - 1) x 6 = 96     
 => 12 + 6n - 6 = 96    
 => 6n = 90  
 => n = 15  

aptitude_arithmetic.htm

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