Average problems
- 1. The average of first nine multiples of 3 is?
Options- A. 12.0
- B. 12.5
- C. 15.0
- D. 18.5 Discuss
Correct Answer: 15.0
Explanation:
Average = ( 3 + 6 + 9 + 12 + 15 + 18 + 21 + 24 + 27 ) / 9
= 3(1+2+3+4+5+6+7+8+9)/9
= ( 45 / 3 )
= 15
- 2. The average of five results is 46 and that of the first four is 45. the fifth result is?
Options- A. 51
- B. 50
- C. 49.5
- D. 49 Discuss
Correct Answer: 49
Explanation:
Fifth result = sum of all five result - sum of first four result.
= 5 x 46 - 4 x 45
= 230 -180
=50
- 3. The average of 30 results is 20 and the average of other 20 results is 30 . what is the average of all the results?
Options- A. 24
- B. 25
- C. 48
- D. 50 Discuss
Correct Answer: 24
Explanation:
Sum of 50 result = sum of 30 result + sum of 20 result.
= 30 x 20 + 20 x 30
= 1200
- 4. The average of numbers 0.64204, 0.64203, 0.64202 and 0.64201 is?
Options- A. 0.64202
- B. 0.64204
- C. 0.642022
- D. 0.642025 Discuss
Correct Answer: 0.642025
Explanation:
Average = (0.64204 + 0.64203 + 0.64202 + 0.64201)/ 4
=2.5681/ 4
=0.642025
- 5. The average weight of A, B, C is 45kg. if the average weight of A and B be 40 kg and that of B and C be 40kg and that of B and C be 43kg, then the weight of B is?
Options- A. 17kg
- B. 20kg
- C. 26kg
- D. 31kg Discuss
Correct Answer: 31kg
Explanation:
weight of (A + B ) = (2 X 40 ) Kg = 80 kg
weight of (B + C ) = (2 X 43) kg = 86 kg
weight of (A + 2B +C ) = (80 + 86) kg = 166 kg
weight of (A + B + C ) = (3 X 45) kg = 135 kg
weight of B = (166-135) kg = 31 kg
- 6. The average weight of 19 students is 15kg. by the admission of a new student the average weight is reduced to 14.8 kg. the weight of the new student is?
Options- A. 10.6 kg
- B. 10.8 kg
- C. 11 kg
- D. 14.9 kg Discuss
Correct Answer: 11 kg
Explanation:
Weight of new student = Total weight of all 20 students - Total weight of initial 19 students
= (20 x 14.8 - 19 x 15) kg
= 11 kg.
- 7. The average weight of 8 persons is increased by 2.5 kg, when one of them whose weight is 56 kg is replaced by a new man. The weight of the man is?
Options- A. 66 kg
- B. 75 kg
- C. 76 kg
- D. 86 kg Discuss
Correct Answer: 76 kg
Explanation:
Total Increase = 8 x 2.5 = 20 kg.
weight of new man = (56 + 20) kg = 76 kg
- 8. The average of the daily income of A, B and C is Rs . 60 . If B earns Rs . 20 more than C and A earns double of what C earns. What is the daily income of C?
Options- A. Rs. 70
- B. Rs. 60
- C. Rs. 40
- D. None of these Discuss
Correct Answer: Rs. 40
Explanation:
Let C's earning = Rs. y.
Then, B's earning = Rs. (y + 20)
and A's earning = Rs. 2y
? 2y + y + 20 + y= 3 x 60
? 4x = 160
? x = 40
- 9. The average age of an adult class is 40 years. 12 new students with an average age of 32 years join the class. Therefore decreasing the average by 4 year. what was the original strength of class?
Options- A. 10
- B. 11
- C. 12
- D. 15 Also asked in: Bank Exams
Correct Answer: 12
Explanation:
Let original strength = y
Then , 40y + 12 x 32 = ( y + 12) x 36
? 40y + 384 = 36y + 432
? 4y = 48
? y = 12
- 10. In a class, there are 20 boys whose average age is decreased by 2 months, when one boy aged 18 years is replaced by a new boy. The age of the new boy is?
Options- A. 14 years 8 months
- B. 15 years
- C. 16 years 4 months years
- D. 17 years 10 months years Discuss
Correct Answer: 14 years 8 months
Explanation:
Total decrease
= ( 20 X 2 ) months
= 3 years 4 month
? Age of the new boy
= ( 18 years ) ? ( 3 years 4 months)
= 14 years 8 month
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