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The average of marks obtained by 120 boys was 35. If the average of marks of passed boys was 39 and that of failed boys was 15, the number of boys who passed the examination is?

A.

100

B.

110

C.

120

D.

130

Answer with explanation

Answer: Option AExplanation

Let the number of boys who passed = X.

Then, 39 x X + 15 x (120 – X) = 120 x 35

24X = 4200 – 1800

=> X = 2400/24

X = 100.

24X = 4200 – 1800

=> X = 2400/24

X = 100.

Hence, the number of boys passed = 100.

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The average age of 20 men in the class is 15.6 years. Five new men join and the new average becomes 15.56 years. What was the average age of five new men?

A.

15.5

B.

15.4

C.

15.25

D.

15.3

Answer with explanation

Answer: Option BExplanation

Total age of 20 men = 15.6 x 20 = 312

Now, total age of 25 men = 389.

Total age of five men added later = 389 – 312 = 77.

Hence, the total average of five men = 77/5 = 15.4

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The average of 50 numbers is 38. If two numbers 45 and 55 are discarded, the average of the remaining set of numbers is

A.

38.5

B.

37.5

C.

37.0

D.

36.5

Answer with explanation

Answer: Option BExplanation

Average of the remaining set of numbers

[50 x 38 – (45 + 55)] / (50 – 2)

= (1900 – 100) / 48

= 37.5

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At Chennai it rained as much on Tuesday as on all the others days of the week combined. If the average rainfall for the whole week was 3 cm. How much did it rain on Tuesday?

A.

2.625 cm

B.

3 cm

C.

10.5 cm

D.

15 cm

Answer with explanation

Answer: Option CExplanation

Total rainfall = 3 x 7 = 21 cm

Hence, rainfall received on Tuesday = 21/2 (as it rained as much on Tuesday as on all the others days of the week combined)

= 10.5 cm.

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A batsman in his 17th innings makes a score of 85, and thereby increases his average by 3. What is his average after the 17th innings? He had never been ’not out’.

A.

47

B.

37

C.

39

D.

43

Answer with explanation

Answer: Option BExplanation

Average score before 17th innings

= 85 – 3 × 17= 34

Average score after 17th innings

=> 34 + 3 = 37

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The average of 17 numbers is 10.9. If the average of first nine numbers is 10.5 and that of the last nine numbers is 11.4, the middle number is

A.

11.8

B.

11.4

C.

10.9

D.

11.7

Answer with explanation

Answer: Option AExplanation

Sum of first nine numbers (N_{1} to N_{9}) + Sum of last nine numbers (N_{9} to N_{17})_{ }= 10.5 x 9 + 11.4 x 9 = 21.9 x 9 = 197.1

Hence, the middle number

= 197.1 – 17 x 10.9

= 197.1 – 185.3 = 11.8

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In a class of 78 students 41 are taking French, 22 are taking German. Of the students taking French or German, 9 are taking both courses. How many students are not enrolled in either course?

A.

6

B.

12

C.

24

D.

18

Answer with explanation

Answer: Option CExplanation

You could solve this by drawing a Venn diagram. A simpler way is to realize that you can subtract the number of students taking both languages from the numbers taking French to find the number taking only French. Likewise find those taking only German. Then we have:Total = only French + only German + both + neither

78 = (41-9) + (22-9) + 9 + neither.

Not enrolled students = 24

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

A.

285

B.

290

C.

297

D.

305

Answer with explanation

Answer: Option AExplanation

Since the month begins with a Sunday, so there will be five Sundays in the month,

Required average = (510 * 5 + 240 * 25) / 30 = 8550/30 = 285

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The average temperature for Monday, Tuesday, Wednesday and Thursday was 48 degrees and for Tuesday, Wednesday, Thursday and Friday was 46 degrees. If the temperature on Monday was 42 degrees. Find the temperature on Friday ?

A.

34

B.

36

C.

38

D.

40

Answer with explanation

Answer: Option AExplanation

M + Tu + W + Th = 4 x 48 = 192

Tu + W + Th + F = 4 x 46 = 184

M = 42

Tu + W + Th = 192 – 42 = 150

F = 184 – 150 = 34

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The average age of students of a class is 15.8 years. The average age of boys in the class is 16.4 years and that of the girls is 15.4 years, The ratio of the number of boys to the number of girls in the class is :

A.

1 : 2

B.

2 : 3

C.

3 : 4

D.

4 : 5

Answer with explanation

Answer: Option BExplanation

Let the ratio be k : 1. Then,

k * 16.4 + 1 * 15.4 = (k + 1) * 15.8

<=> (16.4 – 15.8) k = (15.8 – 15.4) <=> k = 0.4/0.6 = 2/3.

Required ratio = 2/3 : 1 = 2 : 3.

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A.

62 degrees

B.

64 degrees

C.

65 degrees

D.

66 degrees

Answer with explanation

Answer: Option BExplanation

Sum of temperatures on 1st, 2nd, 3rd and 4th days = (58 * 4) = 232 degrees … (1)

Sum of temperatures on 2nd, 3rd, 4th and 5th days – (60 * 4) = 240 degrees ….(2)

Subtracting (1) From (2), we get :

Temp, on 5th day – Temp on 1st day = 8 degrees.

Let the temperatures on 1st and 5th days be 7x and 8x degrees respectively.

Then, 8x – 7x = 8 or x = 8.

Temperature on the 5th day = 8x = 64 degrees.

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The average age of a husband and his wife was 23 years at the time of their marriage. After five years they have a one-year old child. The average age of the family now is :

A.

25

B.

23

C.

19

D.

18

Answer with explanation

Answer: Option CExplanation

Sum of the present ages of husband, wife and child = (23 * 2 + 5 * 2) + 1 = 57 years.

Required average = (57/3) = 19 years.

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Out of 9 persons, 8 persons spent Rs. 30 each for their meals. The ninth one spent Rs. 20 more than the average expenditure of all the nine. The total money spent by all of them was :

A.

Rs. 292.50

B.

Rs. 297.50

C.

Rs. 298

D.

Rs. 298.50

Answer with explanation

Answer: Option AExplanation

Let the average expenditure be Rs. x Then,

9x=[(8*30)+(x+20)]<=>9x =x+260 <=> x =32.50

Total money spent = 9x = Rs. (9 x 32.5O) = Rs 292. 50

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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.

35.5

C.

40

D.

42

Answer with explanation

Answer: Option BExplanation

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

Correct mean = = 1825/50 = 36.5

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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 with explanation

Answer: Option AExplanation

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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