Quantitative Aptitude - Arithmetic Ability Questions

Q:

In the following number series, one of the numbers is wrong. Find it out?

77, 79, 76, 81, 75, 85

A) 79 B) 81
C) 75 D) 85
 
Answer & Explanation Answer: C) 75

Explanation:

Here in the given series, it follows a pattern that

 

77 + 2 = 79

 

79  - 3 = 76

 

76 + 5 = 81

 

81 -  7 = 74

 

74 + 11 = 85

 

Consecutive adding and subtracting of prime numbers.

 

So the wrong number in the given series is 75.

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Filed Under: Odd Man Out
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7 68045
Q:

In 10 years, A will be twice as old as B was 10 years ago. If A is now 9 years older than B, the present age of B is :

A) 19 B) 29
C) 39 D) 49
 
Answer & Explanation Answer: C) 39

Explanation:

Let B's present age = x years. Then, A's present age = (x + 9) years.
(x + 9) + 10 = 2(x - 10)

 => x + 19 = 2x - 20

 => x =39.

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Filed Under: Problems on Ages

346 67943
Q:

The product of two numbers is 2028 and their H.C.F. is 13. The number of such pairs is:

A) 1 B) 2
C) 3 D) 4
 
Answer & Explanation Answer: B) 2

Explanation:

Let the numbers 13a and 13b.

Then, 13a x 13b = 2028

=>ab = 12.

Now, the co-primes with product 12 are (1, 12) and (3, 4).

[Note: Two integers a and b are said to be coprime or relatively prime if they have no common positive factor other than 1 or, equivalently, if their greatest common divisor is 1 ]

So, the required numbers are (13 x 1, 13 x 12) and (13 x 3, 13 x 4).

Clearly, there are 2 such pairs.

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Filed Under: HCF and LCM

231 67887
Q:

What value will come in place of question mark (?) in the number - series given below  ? 

4, 30, ?, 1440, 7195, 71940

A) 145 B) 545
C) 650 D) 999
 
Answer & Explanation Answer: A) 145

Explanation:

4       30       ?     1440       7195      71940

 

Here the given series follows a pattern of

 

4

 

4 x 10 - 10 = 30

 

30 x 5 - 5  = 145

 

145 x 10 - 10 = 1440

 

1440 x 5 - 5 = 7195

 

7195 x 10 - 10 = 71940

 

Hence, the missing number is 145

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Q:

Find the Odd One Out?

4, 6, 12, 30, 81, 315.

A) 6 B) 12
C) 81 D) 315
 
Answer & Explanation Answer: C) 81

Explanation:

Given the number series is 4, 6, 12, 30, 81, 315.

Here it follows a pattern that

4

4 x 1.5 = 6

6 x 2 = 12

12 x 2.5 = 30

30 x 3 = 90 not equals to 81

90 x 3.5 = 315

 

Hence the odd one in the series is 81.

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9 67504
Q:

A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is :

A) 9.5 km/hr B) 10 km/hr
C) 10.5 km/hr D) 11 km/hr
 
Answer & Explanation Answer: B) 10 km/hr

Explanation:

Man's rate in still water = (15 - 2.5) km/hr = 12.5 km/hr.

Therefore,  Man's rate against the current = (12.5 - 2.5) = 10 km/hr.

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Filed Under: Problems on Trains
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109 67455
Q:

An air conditioner can cool the hall in 40 miutes while another takes 45 minutes to cool under similar conditions. If both air conditioners are switched on at same instance then how long will it take to cool the room approximately ?

A) 18 minutes B) 19 minutes
C) 22 minutes D) 24 minutes
 
Answer & Explanation Answer: C) 22 minutes

Explanation:

Let the two conditioners be A and B

 

'A' cools at 40min

 

'B' at 45min

 

Together = (a x b)/(a + b)

= (45 x 40)/(45 + 40)

= 45 x 40/85

= 21.1764

= 22 min (approx).

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Filed Under: Time and Work
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92 67413
Q:

Simplify the fraction?

5 (2/7) - 3 (1/14) - 2 (1/14) - 1 (1/7) = ? + 3 (1/17) 

A) -4 (1/17) B) 5 (2/17)
C) -2 (1/17) D) 3 (3/17)
 
Answer & Explanation Answer: A) -4 (1/17)

Explanation:

Given fraction is 5 (2/7) - 3 (1/14) - 2 (1/14) - 1 (1/7) = ? + 3 (1/17) 

It can be written as 

(5 - 3 - 2 - 1) + (2/7 - 1/14 - 1/14 - 1/7) = ? +  3 (1/17) 

-1 + 0 - 3 (1/17) = ?

=> ? = -4 (1/17)

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Filed Under: Simplification
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