Average problems
- 1. The average of 9 results is 50. The average of the first four results is 52 and the average of the last four results is 49. what is the fifth result?
Options- A. 48
- B. 46
- C. 52
- D. 44 Discuss
Correct Answer: 46
Explanation:
Total of first four results = 52 x 4 = 208
Total of Last four results = 49 x 4 = 196
Hence the fifth result = 450 - (208 + 196) = 46
- 2. 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
Correct Answer: 75
Explanation:
Average = (76 + 65 + 82 + 67 + 85 )/ 5 = 375/5 = 75.
- 3. The average price of three items of furniture is Rs. 15000. If their prices are in the ratio 3:5:7, the price of the cheapest item is :
Options- A. 6000
- B. 7000
- C. 8888
- D. 9000 Discuss
Correct Answer: 9000
Explanation:
Let their prices be 3x, 5x and 7x.
Then, 3x + 5x + 7x = (15000 * 3) or x = 3000.
Cost of cheapest item = 3x = Rs. 9000.
- 4. In a mens hostel, there were 95 students. To accommodate 30 more students the average is decreased by rupees 5. But total expenditure increased by Rs.500. Find the total expenditure of the hostel now ?
Options- A. Rs. 4680
- B. Rs. 4420
- C. Rs. 4960
- D. Rs. 5480 Also asked in: AIEEE, Bank Exams, CAT, GATE, Bank Clerk, Bank PO
Correct Answer: Rs. 4680
Explanation:
Let the expenditure on the 95 students be 'x'
Then,
95x + 500 = 120(x ? 5)
95x + 500 = 120x - 600
120x - 95x = 1100
25x = 1100
=> x = 44
Therefore, total expenditure of the hostel becomes
95 x 44 + 500 = 4680.
- 5. 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
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
- 6. 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 Also asked in: AIEEE, Bank Exams, CAT, GATE, Analyst, Bank Clerk, Bank PO
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
- 7. 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 Also asked in: AIEEE, Bank Exams, CAT, GATE, GRE, Analyst, Bank Clerk, Bank PO
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.
- 8. 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 Also asked in: AIEEE, Bank Exams, CAT, GATE, Bank Clerk, Bank PO
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.
- 9. 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
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.
- 10. 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
Correct Answer: 37.5
Explanation:
Average speed = (2xy) /(x + y) km/hr
= (2 * 50 * 30) / (50 + 30) km/hr.
37.5 km/hr.
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