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Aptitude - Arithmetic Online Quiz

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.

Q 1 - If n^th term of the series 72, 63, 54, ... is 0. What is n?

Answer : B

Explanation

     
Here a = 72,  d = 63 - 72 = -9,      
Using formula T_n = a + (n - 1)d      
T_n = 72 + (n - 1) x -9 = 0      
=> 81 - 9n = 0     
=> n = 9

Q 2 - How many numbers from 29 to 98 are exactly divisible by 9?

Answer : A

Explanation

  
29/9 = 3 and 98/9 = 10  
=> 10 - 3 =7.

Q 3 - How many digits are required to write numbers between 1 to 50?

Answer : B

Explanation

  
 1 to 9       ------ 9 digits  
 10 to 50   ------ 82 digits

Q 4 - If 12³ is subtracted from the square of a number, the answer so obtained is 976. What is the number?

Answer : D

Explanation

  
 Let the number be x.  
 According to question:       
 x² - 12³ = 976  
 or, x = 52

Q 5 - If first term of an A.P. is 6, its common difference is 5 then what is its 11^th term?

Answer : D

Explanation

 
 Here numbers are 14, 21, ..., 196 which is an A.P. 
 Here a = 6,  d = 5,    
 Using formula T_n = a + (n - 1)d    
 T₁₁ = 6 + (11 - 1) x 5 = 56

Q 6 - What is the sum of all odd numbers between 100 and 200?

Answer : D

Explanation

  
 Required sum = 101 + 103 + ... + 199 which is an A.P. where a = 101, d = 2, l = 199.  
 Using formula T_n = a + (n - 1)d  
 T_n = 101 + (n-1)2 = 199  
 => 2n = 199 - 99 = 100  
 => n = 50  
 Now Using formula S_n = (n/2)(a + l)  
 ∴ Required sum = (50/2)(101+199)  = 50 x 150  = 7500

Q 7 - If 2^th and 5^th terms of a G.P. are 2/3 and 16/81 then what will be the 7^th term?

Answer : D

Explanation

   
 Using formula T_n = ar^{n- 1}  
 T₂ = ar^{(2 - 1)}  
 => ar = 2/3 ... (i)  
 T₅ = ar^{(5 - 1)}  
 => ar⁴ = 16/81 ... (ii)  
 Dividing (ii) from (i)  
 => r³ = (2/3) x (81/16)  
 = 9/8 = (2/3)³  
 => r = 2/3  
 Using (i)  a = (2/3) / (2/3) = 1  
 => T₇ = ar^{(7 - 1)}  
 = (2/3)⁽⁶⁾  
 = 64/729

Q 8 - (1³ + 2³ ... + 15³) = ?

Answer : D

Explanation

  
 Using formula  (1³ + 2³ ... +  n³) = [(1/2)n(n+1]²  
 (1³ + 2³ ... + 15³) 
 = [(15 x 16)/2]²  
 = 120²  = 14400

Q 9 - What is the 15^th term of A.P. 14, 9, -1, -6 ... ?

Answer : C

Explanation

 Here a = 14, d = 9 - 14 = -5, n = 15 
 Using formula T_n = a + (n - 1)d 
 T₁₅ = 14 + (15 - 1) x -5 
 = -56

Q 10 - If population of a bacteria doubles every 2 minutes. In how much minutes, it will grow from 1000 to 1024000?

Answer : A

Explanation

   
 Let the required growth be 1000, 2000, 4000,...1024000.  
 Here, a = 1000, r = 2, T_n = 512000  
 Using formula T_n = ar^n-1  
 => 1000 x 2^n-1 = 1024000  
 => 2^n-1 = 1024 = 2¹⁹  
 => n - 1 = 10  => n = 11 
 ∴ time taken will be 2 x 10 = 20 minutes.

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