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A student was asked to find the arithmetic mean of the numbers 3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14 and x. He found the mean to be 12. What should be the number in place of x ?

A.

9

B.

6

C.

8

D.

7

Answer with explanation

Answer: Option DExplanation

Clearly, we have (3 + 11 + 7 + 9 + 15 + 13 + 8 + 19 + 17 + 21 + 14 + x) / 12 = 12.

or 137 + x = 144 or x = 144 – 137 = 7.

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The average monthly income of P and Q is Rs. 5050. The average monthly income of Q and R is Rs. 6250 and the average monthly income of P and R is Rs. 5200. The monthly income of P is:

A.

4000

B.

5000

C.

4050

D.

3500

Answer with explanation

Answer: Option AExplanation

Let P, Q and R represent their respective monthly incomes. Then, we have:

P + Q = (5050 x 2) = 10100 …. (i)

Q + R = (6250 x 2) = 12500 …. (ii)

P + R = (5200 x 2) = 10400 …. (iii)

Adding (i), (ii) and (iii), we get: 2(P + Q + R) = 33000 or P + Q + R = 16500 …. (iv)

Subtracting (ii) from (iv), we get P = 4000.

P’s monthly income = Rs. 4000.

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The average age of a family of 5 members is 20 years. If the age of the youngest member be 10 years then what was the average age of the family just a day before the birth of the youngest member?

A.

14 years

B.

13.5 years

C.

10 years

D.

12.5 years

Answer with explanation

Answer: Option DExplanation

At present the total age of the family = 5 * 20 = 100

The total age of the family at the time of the birth of the youngest member = [100-10-(10*4)] = 50

Therefore, average age of the family at the time of birth of the youngest member = 50/4 = 12.5.

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A library has an average of 510 visitors on Sundays and 240 on other day. The average number of visitors in a month of 30 days starting with sunday is

A.

290

B.

295

C.

285

D.

280

Answer with explanation

Answer: Option CExplanation

As the month begin with sunday, so there will be five sundays in the month. So result will be

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The mean of 50 observations was 36. It was found later that an observation 48 was wrongly taken as 23. The corrected new mean is :

A.

35

B.

42

C.

36.5

D.

30

Answer with explanation

Answer: Option CExplanation

Correct Sum = (36 * 50 + 48 – 23) = 1825.

Correct mean = = 1825/50 = 36.5

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When a student weighing 45 kgs left a class, the average weight of the remaining 59 students increased by 200g. What is the average weight of the remaining 59 students?

A.

58.2

B.

52.2

C.

56.8

D.

57

Answer with explanation

Answer: Option DExplanation

Let the average weight of the 59 students be A.

Therefore, the total weight of the 59 of them will be 59A.

The questions states that when the weight of this student who left is added, the total weight of the class = 59A + 45

When this student is also included, the average weight decreases by 0.2 kgs.

= A – 0.2

=> 59A + 45 = 60A – 12

=> 45 + 12 = 60A – 59A

=> A = 57.

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The average of four consecutive even numbers is 27. Find the largest of these numbers

A.

34

B.

32

C.

30

D.

28

Answer with explanation

Answer: Option CExplanation

Consider the consecutive even numbers as : x, (x + 2), (x + 4) and (x+ 6)

Simplifying we get, x = 24

Therefore,

Largest number = (x + 6) = (24 + 6) = 30

Smallest number = 24

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