Quantitative Aptitude - Arithmetic Ability Questions

Q:

The incomes of two persons A and B are in the ratio 3:4. If each saves Rs.100 per month, the ratio of their expenditures is 1:2. Find their incomes  ?

A) 200, 400 B) 100, 300
C) 100, 200 D) 150, 200
 
Answer & Explanation Answer: D) 150, 200

Explanation:

The incomes of A and B be 3P and 4P.

Expenditures = Income - Savings

(3P - 100) and (4P - 100)

The ratio of their expenditure = 1:2

(3P - 100):(4P - 100) = 1:2

2P = 100 => P = 50

Their incomes = 150, 200

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Filed Under: Ratios and Proportions
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Q:

A wheel that has 6 cogs is meshed with a larger wheel of 14 cogs. When the smaller wheel has made 21 revolutions, then the number of revolutions made by the larger wheel is ?

A) 11 B) 7
C) 9 D) 13
 
Answer & Explanation Answer: C) 9

Explanation:

Here the number of cogs is inveresly proportional to number of revolutions

=> More cogs less revolution
=> 6 : 14 :: x : 21
=> (21x6)/14 = 9

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Q:

Raghu can do a job in 12 days alone and Sam can do the same job in 15 days alone. A third person Aru whose efficiency is two-third of efficiency of both Ram and Shyam together, can do the same job in how many days alone?

A) 10 B) 12
C) 13 D) 15
 
Answer & Explanation Answer: A) 10

Explanation:

One day work of Raghu and Sam together = 1/12 + 1/15 = 9/60 = 3/20

Aru efficiency = 2/3 of (Raghu + Sam)

Number of days required for Aru to do thw work alone = 3/2 x 20/3 = 10 days. 

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Filed Under: Time and Work
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Q:

Consider 5 independent Bernoulli’s trials each with probability of success p. If the probability of at least one failure is greater than or equal to 31/32 , then p lies in the interval ?

A) [1, 32] B) (0, 1)
C) [1, 1/2] D) (1, 1/2]
 
Answer & Explanation Answer: C) [1, 1/2]

Explanation:

Probability of atleast one failure
= 1 - no failure > 31/32
= 1 - P5 > 31/32
=  P5<1/32
= p < 1/2
Also p > 0
Hence p lies in [0,1/2].

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Q:

Adam and Smith are working on a project. Adam takes 6 hrs to type 36 pages on a computer, while Smith takes 5 hrs to type 40 pages. How much time will they take, working together on two different computers to type a project of 120 pages?

A) 8 hrs 45 min B) 8 hrs 42 min
C) 8 hrs D) 8 hrs 34 min
 
Answer & Explanation Answer: D) 8 hrs 34 min

Explanation:

Number of pages typed by Adam in 1 hour = 36/6 = 6
Number of pages typed by Smith in 1 hour = 40/5 = 8
Number of pages typed by both in 1 hour = (6 + 8) = 14
Time taken by both to type 110 pages = (120 * 1/14) = 847 = 8 hrs 34 min.

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Q:

'K' cycled from A to B at 10 kmph and returned at the rate of 9 kmph. 'L' cycled both ways at 12 kmph. In the whole journey 'L' took 10 minutes less than 'K'. Find the distance between A and B ?

A) 32.1 km B) 15.23 km
C) 3.75 km D) 32.1 m
 
Answer & Explanation Answer: C) 3.75 km

Explanation:

Let 'd' be the distance between A and B
K -time = d/10 + d/9 = 19d/90 hours
L -time = 2d/12 = d/6 hours
We know that, 10 min = 1/6 hours
Thus, time difference between K and L is given as 10 minutes.
=> 19d/90 - d/6 = 1/6
=> (19d-15d)/90 = 1/6
=> 4d/90 = 1/6
Thus,
d= 15/4 km = 3.75 km.

hence the distance between A and B is 3.75 km.

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Q:

Ajay and his wife Reshmi appear in an interview for two vaccancies in the same post. The Probability of Ajay's selection is 1/7 and that of his wife Reshmi's selection is 1/5. What is the probability that only one of them will be selected?

A) 5/7 B) 1/5
C) 2/7 D) 2/35
 
Answer & Explanation Answer: C) 2/7

Explanation:

P( only one of them will be selected) = p[(E and not F) or (F and not E)] 

 = PEFFE 

 

PEPF+PFPE

 

 =17×45+15×67=27

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Q:

The average age of a group of 10 students is 15 years. When 5 more students join the group, the average age increase by 1 year. The average age of the new student is?

Answer

Total age of 10 students = 150 years


Total age of 15 students = 240 years


Total age of 5 new students = 240 - 150 = 90 years


 Average age of 5 new students = 90/5 = 18 years.

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Subject: Problems on Ages

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