Average problems
- 1. A batsman has a certain average of runs for 14th innings. He scores 72 runs in the 15th innings, thus his average increased by 2. Find the average after 15th innings.
Options- A. 44
- B. 46
- C. 42
- D. 48 Discuss
Correct Answer: 44
Explanation:
Let the average of 14th innings = x
? Average of 15th innings = x+2
Then, 14x+72 = 15(x+2)
? 14x+72 = 15x +30
? x = 42
? Average for 15th innings = x+2 = 42 + 2 = 44
- 2. The Average of 5 observation is 15. If three new observation 16.5, 18 and 14.5 be added. Then find the new average.
Options- A. 14.8
- B. 15.5
- C. 16.2
- D. 15.6 Discuss
Correct Answer: 15.5
Explanation:
Total of 5 observations = 5 x 15 = 75
New sum = 75 + 16.5 + 18 + 14.5 = 124
New Average = 124 ? 8 = 15.5
- 3. The average of x 1, x 2 and x 3 is 14. Twice the sum of x 2 and x 3 is 30. What is the value of x 1?
Options- A. 20
- B. 27
- C. 16
- D. 2 Discuss
Correct Answer: 27
Explanation:
x1 + x2 + x3 = 3 x 14 = 42 ....(i)
and (x1 + x2) x 2 = 30
? x1 + x2 =15 ....(ii)
From Eqs. (i) and (ii), we get
x1 + 15 = 42
? x1 = 42 - 15 = 27
- 4. The average age of 45 students in a class in 13 yr, 15 new students with an average age of 18 yr join the class. What is the average age of all the students in the class?
Options- A. 13.15 yr
- B. 14.25 yr
- C. 12.28 yr
- D. 16.42 yr Discuss
Correct Answer: 14.25 yr
Explanation:
Sum of the age of 45 students = 45 x 13 = 585 yr
Sum of the age of 15 students = 15 x18 = 270 yr
Sum of the age of all students = sum of the age of 45 students + sum of the age of 15 students
= 585 yr + 270 yr
=855 yr
? Average age of all students = 855 ? 60
= 14.25 yr
- 5. The average salary of the entire staff in an office is ? 200 per day. The average salary of officers is ? 550 and that of non officers is ? 120. If the number of officers is 16, then find the number of non officers in the office.
Options- A. 72
- B. 60
- C. 70
- D. 65 Discuss
Correct Answer: 70
Explanation:
Let the number of non-officers be y.
Then number of entire staff = 16 + y
Sum of total salary = 200(16 + y)
=16 x 550 + 120y
? 120y + 550 x 16 = 200x16 + 200y
? 3y +220 = 80 + 5y
? 2y = 140
? y = 140/2 = 70
- 6. Average value of property of three persons A, B, C is ? 11111 crore. The property of C is as less as the property of A is greater than the average property of both C and A. The value of property of B is.
Options- A. 110 crore
- B. 11211 crore
- C. 11111 crore
- D. 21410 crore Discuss
Correct Answer: 11111 crore
Explanation:
( A + B + C ) / 3 = 11111 ....(i)
Also, ( A+C ) / 2 = 11111 ....(ii)
From Eqs. (i) & (ii), we get
B = ? 11111 crore
- 7. The average age of 25 girls in a class decreases by 6 months when a new girl takes the place of 20 year old girl. Find out the age of the new girl.
Options- A. 7.5 yr
- B. 8.5 yr
- C. 9 yr
- D. 6 yr Discuss
Correct Answer: 7.5 yr
Explanation:
Total decrease in the age = 25 x 1/2 =12.5 yr
? Age of new girl = 20 - 12.5
= 7.5 yr
- 8. The average age of all the members of a family is 25 yr. The average age of males is 30 yr while the average age of females is 20 yr. If the number of females in the family is 15, then find out the number of males.
Options- A. 20
- B. 30
- C. 15
- D. 18 Discuss
Correct Answer: 15
Explanation:
Let number of males = y
Then, total number of family members = 15 + y
Sum of age of family members = sum of age of males + sum of age of females
25(15 + y) = 30y + 15x20
? 375 + 25y = 30y + 300
? 5y = 75
? y = 15
- 9. Out of three annual exams, each of maximum marks of 600, Lalit secured average marks of 55% and 60% in the first two exams. How many marks should Lalit score in 3rd test exam to make his overall average equal to 70%?
Options- A. 560
- B. 570
- C. 590
- D. 500 Discuss
Correct Answer: 570
Explanation:
Total required marks in the three examinations = (3 x 600 x 70)/100 =1260
Marks secured in first examination = 55% of 600 = ( 600 x 55)/100 =330
Marks secured in second examination = 60% of 600 = ( 600 x 60)/100 =360
Thus, the required marks in third examination = 1260 - (330 + 360)
= 1260 - 690
= 570
- 10. The mean marks of 30 students in a class is 58.5. Later on, it was found that 75 was wrongly recorded as 57. Find the correct mean.
Options- A. 57.4
- B. 57.5
- C. 58.9
- D. 59.1 Discuss
Correct Answer: 59.1
Explanation:
Correct mean = ( sum of total marks - 57 + 75 ) / 30
= ( 30 x 58.5 - 57 + 75 ) / 30
= (1755 + 18 ) / 30
= 59.1
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