Average problems
- 1. The average of 10 number is calculate as 15. It is discovered later on that while calculating the average one number , namely 36 was wrongly read as 26. The correct average is?
Options- A. 12.4
- B. 14
- C. 16
- D. 18.6 Discuss
Correct Answer: 16
Explanation:
New sum of numbers = previous sum - 26 + 36
=10 x 15 - 26 + 36
= 160
? Correct Average = 160 / 10 = 16.
- 2. The average of 13 result is 68. The average of first seven is 63 and that of the last seven is 70 , the seventh result is?
Options- A. 47
- B. 65.5
- C. 73.5
- D. 94 Discuss
Correct Answer: 47
Explanation:
Seventh Result = sum of first 7 results + sum of last 7 results - sum of all 13 results.
? Seventh Result = (7 x 63) + (7 x 70) - (13 x 68 )
=47
- 3. The average of 25 results is 18, that of first twelve is 14 and of last twelve is 17 . Thirteenth result is?
Options- A. 28
- B. 72
- C. 78
- D. 85 Discuss
Correct Answer: 78
Explanation:
Thirteenth Result = sum of all 25 results - sum of first 12 results - sum of last 12 results.
= 25 x 18 - 12 x 14 ? 12 x 17
=78
- 4. The average temperature of Monday, Tuesday, Wednesday, and Thursday was 38° C and that of Tuesday, Wednesday, Thursday and Friday was 40° C, if the temperature on Monday was 30° C, the temperature of Friday was?
Options- A. 40°
- B. 39°
- C. 38°
- D. 30° Discuss
Correct Answer: 38°
Explanation:
From question
M + T + W + TH = 4 x 38° = 152°
? T + W + TH =152° ? 30° = 122°
Again from question
? T + W + TH + F = 4 x 40° = 160°
? F = 160° ? 122°
= 38°
- 5. The average of 5 consecutive number is n , if the next two number are also include, the average of 7 number will?
Options- A. Increase by 2
- B. increase by 1
- C. Remains the same
- D. Increase by 1.4 Discuss
Correct Answer: increase by 1
Explanation:
Sum of 5 consecutive integers
x + ( x +1 ) + ( x +2 ) + ( x + 3 ) + ( x +4 ) = 5n
? 5x + 10 = 5n
? x = ( n ? 2 ) ......(i)
Average of 7 consecutive integers
= [( 5x + 10 ) + ( x + 5 ) + ( x + 6 )] / 7
= 7x + 21 / 7
= x + 3 .....(ii)
from eq. (i) and (ii)
New average = x + 3 = ( n ? 2 + 3 ) = n + 1
So , the new average increases by 1 .
- 6. A man whose bowling average is 12.4 takes 5 wicket for 26 runs and thereby decreases his average by 0.4. The number of wickets taken by him, before his last match is?
Options- A. 85
- B. 78
- C. 72
- D. 64 Discuss
Correct Answer: 85
Explanation:
Let the number of wickets taken before the last match = y
Bowler's overall average = total run scored / total wicket taken by bowler
Then, (12.4y + 26 ) / (y + 5) = 12
? x = 85
- 7. There were 35 students in a hostel. If the number of students increased by 7, the expenses of the mess were increase by Rs 42 per Day , while the average expenditure per head diminished by Re. 1 The original expenditure of the mess was?
Options- A. Rs. 40
- B. Rs . 420
- C. Rs . 432
- D. Rs . 442 Discuss
Correct Answer: Rs . 420
Explanation:
Let the original expenditure be Rs. y per day ,
Then, y / 35 - [( y + 42 ) / 42 ] = 1
? 42y - 35 ( y + 42 ) = 35 x 42
? 7y = 35 x 42 + 35 x 42
? y = ( 2 x 35 x 42 ) / 7
= 420
Hence , the original expenditure is Rs . 420
- 8. The average age of a husband and a wife was 23 year when they were married 5 year ago. The average age of the husband, the wife and child, who was born during the interval is 20 years now . How old is the child now?
Options- A. less then 1 year
- B. 1 year
- C. 3 year
- D. 4 year Discuss
Correct Answer: 4 year
Explanation:
Age of child = sum of age of husband , wife and child - sum of age of husband and wife.
= [(20 x 3) - (23 x 2 + 5 x 2)] years
= 4 years.
- 9. Ten years ago the average age of a family of 4 members was 24 years. Two children having been born average age of the family is same today. What is the present age of the youngest child if they differ in age by 2 years?
Options- A. 1 year
- B. 2 years
- C. 3years
- D. 5 years Discuss
Correct Answer: 3years
Explanation:
Let the age of youngest child be y.
Then y + ( y + 2 ) = ( 24 x 6 ) - ( 24 x 4 + 4 x 10)
= 144 - 136
? 2y + 2 = 8
? y =3 years
- 10. The mean temperature of Monday to Wednesday was 37° C and of Tuesday to Thursday was 34° C . If in the temperature on Thursday was 4/5 th that of Monday, what was temperature on Thursday?
Options- A. 34° C
- B. 35.5° C
- C. 36° C
- D. 36.5° C Discuss
Correct Answer: 36° C
Explanation:
M + T + W = 3 x 37 = 111° C .....(1)
T + W + Th = 3 x 34 = 102 ° C ......(ii)
Let M = y
Then, Th = 4y/5
subtraction (ii) from (i) we get,
M - Th = 9° C
? y - 4y / 5 = 9° C
? y = 45° C
? Temperature on thursday = (4 x 45) / 5° C
= 36° C
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