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- Question
The average age of 15 students of a class is 15 years. Out of these, the average age of 5 students is 14 years and that of the other 9 students is 16 years, The age of the 15th student is :
Options- A. 11
- B. 12
- C. 13
- D. 14
- Correct Answer
- 11
ExplanationAge of the 15th student = [15 * 15 - (14 * 5 + 16 * 9)] = (225-214) = 11 years.
- 1. In Arun's opinion, his weight is greater than 65 kg but leas than 72 kg. His brother does not agree with Arun and he thinks that Arun's weight is greater than 60 kg but less than 70 kg. His mother's view is that his weight cannot be greater than 68 kg. If all of them are correct in their estimation, what is the average of diferent probable weights of Arun ?
Options- A. 55.5 kg
- B. 66.5 kg
- C. 77.5 kg
- D. 88.5 kg Discuss
- 2. The average age of 7 boys is increased by 1 year when one of tem whose age is replaced by a girl. What is the age of the girl ?
Options- A. 33 yrs
- B. 27 yrs
- C. 21 yrs
- D. 29 yrs Discuss
- 3. Without any stoppage, a person travels a certain distance at an average speed of 42 km/h, and with stoppages he covers the same distance at an average speed of 28 km/h. How many minutes per hour does he stop?
Options- A. 15 minutes
- B. 20 minutes
- C. 18 minutes
- D. 22 minutes Discuss
- 4. The mean of 100 observations is 40. It is found that an observation 84 was misread as 48. Then the correct mean is ?
Options- A. 40.36
- B. 41.24
- C. 41.92
- D. 42.05 Discuss
- 5. David obtained 76, 65, 82, 67 and 85 marks (out of 100) in English, Mathematics,Physics, Chemistry and Biology What are his average marks ?
Options- A. 75
- B. 68
- C. 65
- D. 60 Discuss
- 6. The ratio of speeds of a car, a train and a bus is 5:9:4. The average speed of the car, the bus and the train is 72 km/hr together. What is the average speed of the car and the train together ?
Options- A. 84 km/hr
- B. 96 km/hr
- C. 72 km/hr
- D. 60 km/hr Discuss
- 7. Out of three numbers, the first is twice the second and is half of the third. If the average of the three numbers is 56, what will be the sum of the highest number and the lowest number?
Options- A. 120
- B. 160
- C. 80
- D. 60 Discuss
- 8. The average age of a group of persons going for picnic is 16 years. Twenty new persons with an average age of 15 years join the group on the spot due to which their average age becomes 15.5 years. The number of persons initially going for picnic is :
Options- A. 15
- B. 20
- C. 23
- D. 24 Discuss
- 9. A motorist travels to a place 150 km away at an average speed of 50 km/hr and returns at 30 km/hr. His average speed for the whole journey in km/hr is :
Options- A. 35
- B. 36
- C. 37.5
- D. 38.2 Discuss
- 10. After replacing an old member by a new member, it was found that the average age of five members of a club is the same as it was 3 years ago. The difference between the ages of the replaced and the new members?
Options- A. 16 years
- B. 15 years
- C. 14 years
- D. 13 years Discuss
Average problems
Search Results
Correct Answer: 66.5 kg
Explanation:
Let Arun's weight be X kg.
According to Arun, 65 < X < 72.
According to Arun's brother, 60 < X < 70.
According to Arun's mother, X < 68.
The values satisfying all the above conditions are 66 and 67.
Required average = (66 + 67) / 2 = 66.5 kg
Correct Answer: 29 yrs
Explanation:
Let the avg age of 7 boys be 'p' years
Let the age of the girl be 'q' years
From given data,
The age of 7 boys = 7p years
Now the new average = (p + 1) when 22 yrs is replaced by q
Now the age of all 7 will become = 7(p + 1) yrs
Hence, 7p - 22 + q = 7(p + 1) yrs
7p - 22 + q = 7p + 7
q = 22 + 7 = 29
Therefore, the age of girl = q = 29 years.
Correct Answer: 20 minutes
Explanation:
Let the total distance to be covered is 84 kms.
Time taken to cover the distance without stoppage = 84/42 hrs = 2 hrs
Time taken to cover the distance with stoppage = 84/28 = 3 hrs.
Thus, he takes 60 minutes to cover the same distance with stoppage.
Therefore, in 1 hour he stops for 20 minutes.
Correct Answer: 40.36
Explanation:
Given,
mean of 100 observations is 40
=> Total of 100 observations = 40 x 100 = 4000
84 is misread as 48
=> Difference = 84 - 48 = 36
=> Now, new total of 100 observations = 4000 + 36 = 4036
Correct Mean = 4036/100 = 40.36
Correct Answer: 75
Explanation:
Average = (76 + 65 + 82 + 67 + 85 )/ 5 = 375/5 = 75.
Correct Answer: 84 km/hr
Explanation:
Let the speeds of the car, train and bus be 5x, 9x and 4x km/hr respectively.
Average speed = 5x + 9x + 4x/3 = 18x /3 = 6x km/hr.
Also, 6x = 72 => x = 12 km/hr
Therefore, the average speed of the car and train together is =
= 7x = 7 x 12 = 84 km/hr.
Correct Answer: 120
Explanation:
Let the three numbers be x, y, z.
From the gien data,
x = 2y ....(1)
x = z/2 => z = 2(2y) = 4y .....(From 1) ...........(2)
Given average of three numbers = 56
Then,
Now,
x = 2y => x = 2 x 24 = 48
z = 4y = 4 x 24 = 96
Now, the highest number is z = 96 & smallest number is y = 24
Hence, required sum of highest number and smallest number
= z + y
= 96 + 24
= 120.
Correct Answer: 20
Explanation:
Let the initial number of persons be x. Then,
16x + 20 * 15 = 15.5 (x + 20) <=> 0.5x = 10 <=> x = 20.
Correct Answer: 37.5
Explanation:
Average speed = (2xy) /(x + y) km/hr
= (2 * 50 * 30) / (50 + 30) km/hr.
37.5 km/hr.
Correct Answer: 15 years
Explanation:
Let avg ages of 5 members at present is G
And age of new member is m and an older is n
Required = (5G + m - n)/5 = G - 3
m - n = 15 years
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