Average problems
- 1. The average weight of a class of 40 students is 40 kg. If the weight of the teacher be included , the average weight increases by 500 gm . The weight of the teacher is?
Options- A. 40.5 kg
- B. 60 kg
- C. 60.5 kg
- D. 62 kg Discuss
Correct Answer: 60.5 kg
Explanation:
Weight of the teacher = Total weight of 40 students and teacher - total weight of 40 students
= 41 x 40.5 - 40 x 40 kg
= 60.5kg
- 2. The average age of four players is 18.5 years. If the age of the coach is also included, the average age increases by 20%. The age of the coach is?
Options- A. 28 years
- B. 31 years
- C. 34 years
- D. 37 years Discuss
Correct Answer: 37 years
Explanation:
New average = 120% of old average
=120% of 18.5
= (120 x 18.5) / 100
= 22.2
Age of coach = Total weight of 4 players and coach - total weight of 4 players
= 5 x 22.2 - 4 x 18.5
= 37 years
- 3. The average age of four children in a family is 12 years. If the spacing between their ages is 4 years, the age of the youngest child is?
Options- A. 6 years
- B. 7 years
- C. 8 years
- D. 9 years Discuss
Correct Answer: 6 years
Explanation:
Let the age of youngest child be y.
so from question y + (y + 4) + (y + 8) + (y + 12) = 4 x 12
? 4y + 24= 48
? y = 6 years
- 4. In a T.V. factory, an average of 60 TVs are produced per day for the fist 25 days of the months. A few workers fell ill for the next five days reducing the daily average for the month to 58 sets per day . The average production per day for day last 5 days is?
Options- A. 45
- B. 48
- C. 52
- D. 58 Discuss
Correct Answer: 48
Explanation:
Production during these 5 days = Total production in a month - production in first 25 days.
= 30 x 58 - 25 x 60
= 240
? Average for last 5 days = 240 / 5
= 48
- 5. The average of marks obtained by 120 candidates was 35. If the average of marks of passed candidates was 39 and that of failed candidates was 39 and that of failed candidates was 15, the number of candidates who passed the examination is?
Options- A. 100
- B. 110
- C. 120
- D. 150 Discuss
Correct Answer: 100
Explanation:
Let the number of candidate who passed = y
Then, 39y + 15(120 - y) =120 x 35
? 24y= 4200 -1800
? y= 2400 / 24 = 100
- 6. The average age of 30 students in a class is 12 years. The average age of a group of 5 of the students is 10 years and that of another group of 5 them is 14 years. The average age of the remaining students is?
Options- A. 8 years
- B. 10 years
- C. 12 years
- D. 14 years Discuss
Correct Answer: 12 years
Explanation:
Let average of the remaining student be y.
Then from questions ( 5 x 10 ) + ( 5 x 14) + 20y = 30 x 12
? 50 + 70 + 20y = 360
? 20y = 360 ? 120
? 20y = 240
? y = 12.
- 7. A shopkeeper earned Rs. 504 in 12 days. His average income for the first four days was Rs. 40 a day. His average income for the remaining days is?
Options- A. Rs. 40
- B. Rs. 42
- C. Rs. 43
- D. Rs. 45 Discuss
Correct Answer: Rs. 43
Explanation:
Let the average for remaining 8 days be Rs. y a day.
Then, ( 4 x 40 ) + 8y = 504
? 8y = 344
? y = 43
? required average Rs. 43
- 8. The average weight of three men A, B and C is 84 kg. Another man D joins the group and the new average becomes 80 kg if another man E, whose weight is 3kg more than that of D, replace A, then the average weight of B , C, D and E becomes 79 kg. the weight of A is?
Options- A. 70 kg
- B. 72 kg
- C. 75 kg
- D. 80 kg Discuss
Correct Answer: 75 kg
Explanation:
From question
A + B + C = 3 x 84 = 252 ....(i)
A + B + C + D = 4 x 80 = 320 ...(ii)
From eq. (ii) - (i)
D = ( 320 - 252 ) = 68
From question E = D + 3
? E =( 68 + 3 ) = 71
Now , B + C + D + E = 4 x 79 = 316
? B + C + D = 316 ? 71 = 245
So , A = 320 - 245 = 75 kg .
- 9. The average age of a family of 6 member is 22 years . if the age of the youngest member be 7 years , what was the average age of the family at the birth of the youngest member was?
Options- A. 15 years
- B. 17 years
- C. 17.5 years
- D. 18 years Discuss
Correct Answer: 18 years
Explanation:
Total present age of the family = 6 x 22
= 132 years
Total age of the family 7 years ago = 132 - 7 x 6
= 90 years
At that time, the number of members was 5
? Average age at time = 90 / 5 years
= 18 years
- 10. The average height of 40 student is 163 cm. On a particular day, three student A, B, C were absent and the average of the remaining 37 student was found to be 162 cm. if A, B have equal height and the height of C be 2 cm less than that of A, find the height of A?
Options- A. 176 cm
- B. 166 cm
- C. 180 cm
- D. 186 cm Discuss
Correct Answer: 176 cm
Explanation:
Let the height of A , B, C be y cm, y cm and (y - 2) cm respectively
Then, y + y + (y - 2) = 163 x 40 - 162 x 37
? 3y - 2 = 526
? y = 176 cm
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