Quantitative Aptitude - Arithmetic Ability Questions

Q:

If a positive integer n, divided by 5 has a remainder 2, which of the following must be true?

A) n is odd B) n + 1 cannot be a prime number
C) (n + 2) divided by 7 has remainder 2 D) n + 3 is divisible by 5
 
Answer & Explanation Answer: D) n + 3 is divisible by 5

Explanation:

You can find the integers which when divided by 5 have a remainder 2 by adding 2 to all multiples of 5. So we have n = 7 , 12, 17, 22 etc.

From this series we can see that n does not have to be odd.

Also n + 1 can be a prime because, for example, 12 + 1 = 13

And (n + 2) / 7 has a remainder 2 in some cases but not all.

Remember the question asks us for what MUST be true, and we see that none of the statements are true in all cases. However, adding 3 to any of the values of n will always give a multiple of 5.

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Filed Under: Numbers
Exam Prep: GRE

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Q:

The average age of a couple is 24 years when they were married five years ago but now the average age of the husband, wife and child is 20 years(the child was born during the interval). What is the present age of the child ?

A) 2 yrs B) 4 yrs
C) 3 yrs D) 5 yrs
 
Answer & Explanation Answer: A) 2 yrs

Explanation:

29 x 2 = 58
20 x 3 = 60
         -----------
               2 years

Therefore, the age of child is 2 years.

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Filed Under: Problems on Ages
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Q:

The inner circumference of a circular race track, 14m wide is 440m. Find the radius of the outer circle.

A) 84m B) 24m
C) 44m D) 54m
 
Answer & Explanation Answer: A) 84m

Explanation:

let inner radius be r meters. 

2πr=440r=440×744=70mradius of outer circle =70+14m  

 

Therefore, Radius of outer circle = 70 + 14 = 84m

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Filed Under: Area
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Q:

If p:q are the odds in favour of an event,then the probability of that event is:

A) p/q B) p/(p+q)
C) q/(p+q) D) none
 
Answer & Explanation Answer: B) p/(p+q)

Explanation:

Total number of cases=p+q

Favourable cases=p

Probability of that event is=p/(p+q)

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Filed Under: Probability

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Q:

Find the odd man out from the given alternatives ?

A) 97 B) 233
C) 437 D) 599
 
Answer & Explanation Answer: C) 437

Explanation:

Except 437 all others are prime numbers.

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Filed Under: Odd Man Out
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Q:

A coin is tossed twice if the coin shows head it is tossed again but if it shows a tail then a die is tossed. If 8 possible outcomes are equally likely. Find the probability that the die shows a number greater than 4, if it is known that the first throw of the coin results in a tail

A) 1/3 B) 2/3
C) 2/5 D) 4/15
 
Answer & Explanation Answer: A) 1/3

Explanation:

Here Sample space S = { HH, HT, T1, T2, T3, T4, T5, T6 }

 

Let A be the event that the die shows a number greater than 4 and B be the event that the first throw of the coin results in a tail then,

 

 A = { T5, T6 }

 

 B = { T1, T2, T3, T4, T5, T6 }

 

Therefore, Required probability = PAB=PABPB=2868=13

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Q:

The average of the two-digit numbers, which remain the same when the dibits inter-change their positions, is :

A) 53 B) 54
C) 55 D) 56
 
Answer & Explanation Answer: C) 55

Explanation:

Average = (11 + 22 + 33 + 44 + 55 + 66 + 77 + 88 + 99) / 9

             =( (11 + 99) + (22 + 88) + (33 + 77) + (44 + 66) + 55) / 9

             = (4 * 110 + 55)/9 =  495 / 9 = 55. 

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Filed Under: Average

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Q:

If radius and height of a cylinder increase by 20% and15% respectively. then what is the % change in curved surface area?

A) 41% B) 38%
C) 33% D) 44%
 
Answer & Explanation Answer: B) 38%

Explanation:

% Change in Curved Surface Area is given by 

%Change in radius + %Change in height + %Change in radius × %Change in height 100  

+20 + 15 + 20×15100 = 38%

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Filed Under: Volume and Surface Area
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