6500+ Quantitative Aptitude Questions and Answers With Explanation

Q:

If the mean of a, b, c is M and ab + bc + ca = 0, then the mean of $\frac{a^{2} + b^{2} + c^{2}}{3}$ is :

A) M	B) 3 M^2
C) 2 (M/3)	D) M^2

Answer & Explanation Answer: B) 3 M^2

Explanation:

We have : ( a + b + c) / 3 = M or (a + b + c) = 3M.

Now. ${(a + b + c)}^{2} = {(3 M)}^{2} = 9 M^{2}$ .

$< = > a^{2} + b^{2} + c^{2} + 2 (a b + b c + c a) = 9 M^{2}$

$a^{2} + b^{2} + c^{2} = 9 M^{2}, (a b + b c + c a = 0)$

Required mean = $(\frac{a^{2} + b^{2} + c^{2}}{3}) = \frac{9 M^{2}}{3} = 3 M^{2}$ .

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Filed Under: Average
Exam Prep: AIEEE , Bank Exams , CAT
Job Role: Bank Clerk , Bank PO

35 28167

Q:

A bag contains 2 red, 3 green and 2 blue balls. Two balls are drawn at random. What is the probability that none of the balls drawn is blue?

A) 10/21	B) 11/21
C) 1/2	D) 2/7

Answer & Explanation Answer: A) 10/21

Explanation:

Total number of balls = (2 + 3 + 2) = 7.

Let S be the sample space.

Then, n(S) = Number of ways of drawing 2 balls out of 7 = $7 C_{2}$ = 21

Let E = Event of drawing 2 balls, none of which is blue.

n(E) = Number of ways of drawing 2 balls out of (2 + 3) balls = $5 C_{2}$ = 10

Therefore, P(E) = n(E)/n(S) = 10/ 21.

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Filed Under: Probability

37 28141

Q:

A sum of Rs. 725 is lent in the beginning of a year at a certain rate of interest. After 8 months, a sum of Rs. 362.50 more is lent but at the rate twice the former. At the end of the year, Rs. 33.50 is earned as interest from both the loans. What was the original rate of interest?

A) 3.46%	B) 4.5%
C) 5%	D) 6%

Answer & Explanation Answer: A) 3.46%

Explanation:

Let the original rate be R%. Then, new rate = (2R)%.

Note: Here, original rate is for 1 year(s); the new rate is for only 4 months i.e.1/3 year(s).

$(\frac{725 * R * 1}{100}) + (\frac{362.50 * 2 R * 1}{100 * 3}) = 33.50$

=> (2175 + 725) R = 33.50 x 100 x 3

=> (2175 + 725) R = 10050

=> (2900)R = 10050

=> $R = \frac{10050}{2900} = 3.46$

Original rate = 3.46%

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Filed Under: Simple Interest
Exam Prep: GRE

37 28116

Q:

A train travelling at a speed of 75 mph enters a tunnel $3 \frac{1}{2}$ miles long. The train is $\frac{1}{4}$ mile long. How long does it take for the train to pass through the tunnel from the moment the front enters to the moment the rear emerges?

A) 2.5 min	B) 3 min
C) 3.2 min	D) 3.5 min

Answer & Explanation Answer: B) 3 min

Explanation:

Total distance covered = $(\frac{7}{2} + \frac{1}{4})$ miles = $\frac{15}{4}$ miles

Time taken = $(\frac{15}{4 * 75})$ hrs = $\frac{1}{20}$ hrs = $(\frac{1}{20} * 60) m i n$ = 3 min

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Filed Under: Problems on Trains

36 28108

Q:

Consider the following inequalities in respect of any triangle ABC:

1) AC –AB < BC

2) BC –AC < AB

3) AB –BC < AC

Which of the above are correct?

A) 1 and 2 only	B) 2 and 2 only
C) 1 and 3 only	D) 1, 2 and 3

Answer & Explanation Answer: D) 1, 2 and 3

Explanation:

AC-AB<BC Or AB+BC>AC

BC-AC<AB Or AB+AC>BC

AB-BC<AC Or AC+BC>AB

Sum of 2 sides of triangle is always greater than the third side

So all three statements are true

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Filed Under: Volume and Surface Area
Exam Prep: Bank Exams

1 28052

Q:

Three numbers are in the ratio 4 : 5 : 6 and their average is 25. The largest number is :

A) 30	B) 40
C) 50	D) 60

Answer & Explanation Answer: A) 30

Explanation:

Let the numbers be 4x, 5x and 6x, Then, (4x + 5x + 6x ) / 3 = 25

=> 5x = 25

=> x = 5.

Largest number 6x = 30.

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Filed Under: Problems on Numbers

39 28051

Q:

The length of the room is 5.5m and width is 3.75m. Find the cost of paving the floor by slabs at the rate of Rs.800 per sq meter

A) Rs.16500	B) Rs.15500
C) Rs.17500	D) Rs.18500

Answer & Explanation Answer: A) Rs.16500

Explanation:

l=5.5m w=3.75m
area of the floor = 5.5 x 3.75 = 20.625 sq m
cost of paving = 800 x 20.625 = Rs. 16500

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Filed Under: Area
Exam Prep: Bank Exams
Job Role: Bank PO

18 27925

Q:

Selling price of an article is Rs 2397 and discount offered is 15%. What is the marked price (in Rs)?

A) 2756.5	B) 2856.6
C) 2740	D) 2820

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