Quantitative Aptitude - Arithmetic Ability Questions

Q:

In an examination, a student scores 4 marks for every correct answer and loses 1 mark for every wrong answer. If he attempts all 60 questions and secures 130 marks, the no of questions he attempts correctly is :

A) 35 B) 38
C) 40 D) 42
 
Answer & Explanation Answer: B) 38

Explanation:

Let the number of correct answers be X.

Number of incorrect answers = (60 – X).

4x – (60 – x) = 130

=> 5x = 190 

=> x = 38

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Filed Under: Simplification

260 85449
Q:

If each edge of a cube is increased by 50%, find the percentage increase in Its surface area

A) 125% B) 150%
C) 175% D) 110%
 
Answer & Explanation Answer: A) 125%

Explanation:

Let the edge = a cm   

So increase by 50 % = a + a/2 = 3a/2  

Total surface Area of original cube = 6a2  

TSA of new cube = 63a22 =69a24=  13.5a2   

Increase in area = 13.5a2-6a2 =7.5a2  

 7.5a2 Increase % =7.5a26a2×100 = 125%

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477 85078
Q:

The average of 7 consecutive numbers is 20. The largest of these numbers is :

A) 21 B) 22
C) 23 D) 24
 
Answer & Explanation Answer: C) 23

Explanation:

Let the numbers be x, x + 1, x + 2,  x + 3, x + 4, x + 5 and x + 6,

Then   (x + (x + 1) + (x + 2) + (x + 3) + (x + 4) + (x + 5) + (x + 6)) / 7 = 20.

or  7x + 21 = 140 or 7x = 119 or x =17.

Latest number = x + 6 = 23.

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Filed Under: Average

248 84790
Q:

A, B, C started a business with their investments in the ratio 1:3 :5. After 4 months, A invested the same amount as before and B as well as C withdrew half of their investments. The ratio of their profits at the end of the year is :

A) 1 : 2 : 3 B) 3 : 4 : 15
C) 3 : 5 : 10 D) 5 : 6 : 10
 
Answer & Explanation Answer: D) 5 : 6 : 10

Explanation:

Let their initial investments be x, 3x and 5x respectively. Then,

 

A:B:C = (x*4+2x*8) : (3x*4+(3x/2)*8) : (5x*4+(5x/2)*8)

 

20x : 24x : 40x = 5 : 6 : 10          

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Filed Under: Partnership

202 83906
Q:

The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero ?

A) 0 B) -1
C) 1 D) none of these
 
Answer & Explanation Answer: A) 0

Explanation:

Average of 20 numbers = 0. 

 

Sum of 20 numbers = (0 * 20) = 0. 

 

It is quite possible that 19 of these numbers may be positive and if their sum is a, then 20th number is (- a).

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Filed Under: Average

270 81884
Q:

In a 100 m race, A beats B by 10 m and C by 13 m. In a race of 180 m, B will beat C by:

A) 5.4m B) 4.5m
C) 5m D) 6m
 
Answer & Explanation Answer: D) 6m

Explanation:

A : B = 100 : 90.

 

A : C = 100 : 87.

 

B/C = (B/A*A/C) = (90/100*100/87) = 30/29

 

When B runs 30 m, C runs 29 m.

 

When B runs 180 m, C runs (29/30*180)m =174m

 

 B beats C by (180 - 174) m = 6 m.

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Filed Under: Races and Games

100 81712
Q:

Two dice are tossed. The probability that the total score is a prime number is:

A) 5/12 B) 1/6
C) 1/2 D) 7/9
 
Answer & Explanation Answer: A) 5/12

Explanation:

Clearly, n(S) = (6 x 6) = 36.

Let E = Event that the sum is a prime number.

Then E= { (1, 1), (1, 2), (1, 4), (1, 6), (2, 1), (2, 3), (2, 5), (3, 2), (3, 4), (4, 1), (4,3),(5, 2), (5, 6), (6, 1), (6, 5) }

n(E) = 15.

P(E) = n(E)/n(S) = 15/36 = 5/12.

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Filed Under: Probability

198 81255
Q:

What was the day of the week on 28th May, 2006?

A) Sunday B) Friday
C) Wednesday D) Tuesday
 
Answer & Explanation Answer: A) Sunday

Explanation:

28 May, 2006 = (2005 years + Period from 1.1.2006 to 28.5.2006)

 

Odd days in 1600 years = 0

 

Odd days in 400 years = 0

 

5 years = (4 ordinary years + 1 leap year) = (4 x 1 + 1 x 2) = 6 odd days

 

(31[jan] + 28 [Feb]+ 31[Mar] + 30[April] + 28[May] ) = 148 dayss = (21 weeks + 1 day) = 1 odd day.

 

Total number of odd days = (0 + 0 + 6 + 1) = 7 = 0 odd days.

 

Given day is Sunday

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Filed Under: Calendar

419 80807