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- Question
- The mean weight of 150 students in class is 60 kg. The mean weight of boys is 70 kg and that of girls is 55 kg. What is the number of boys in the class?
Options- A. 50
- B. 60
- C. 75
- D. 100
- Correct Answer
- 50
ExplanationGiven that total number of students = 150 = ( n1+ n2) and
Mean weight of 150 students = 60 kg.
The mean weight of boys a1= 70 kg and
The mean weight of girls a2 = 55 kg
Let n1 and n2 be the number of boys and girl, respectively.
? n1 + n2 = 150 ...(i)
11 n1 + 11 n2 = 1650 ...(ii)
Average weight = (n1 a1 + n2 a2) / (n1 + n2)
? 60 = (70 n1 + 55n2)/150
? 70 n1 + 55n2 = 9000
? 14n1 + 11n2 =1800 ...(iii)
On subtracting Eq. (ii) from Eq. (iii), we get
3n1 = 150 ? n1 = 50
Hence, required number of boys is 50. - 1. The average weight of 10 woman is incraesed by 1 kg if 2 woman of 42 kg and 38 kg are replaced by 2 men.Find the average weight of both the men?
Options- A. 46 kg
- B. 45kg
- C. 42 kg
- D. 44 kg Discuss
- 2. The average age of a committee of 11 persons increases by 2 yr when 3 men of 32 yr. 34 yr and 33 yr are replaced by 3 woman. What will be the average age of those 3 woman?
Options- A. 40 yr
- B. 411/3 yr
- C. 41 yr
- D. 401/3 yr Discuss
- 3. The average age of 4 member of a family is 25 yr. If head of the family is included in this group then average age increase by 20%. Find out the age of the head.
Options- A. 45 yr
- B. 50 yr
- C. 55 yr
- D. 60 yr Discuss
- 4. The mean marks obtained by seven students group is 226. If the marks obtained by six of them are 340, 180, 260, 56, 275 and 307 respectively. Find the markes obtained by the seventh student.
Options- A. 164
- B. 226
- C. 340
- D. cannot be determined Discuss
- 5. The average marks of 30 students are 45 but after checking there are two mistakes found. After adjustment if a student got 45 more markes and other student got 15 less marks, then What will be the adjusted average?
Options- A. 45
- B. 44
- C. 47
- D. 46 Discuss
- 6. The average monthly income of 4 earning members of a family is ? 7350. One member passes away and the average monthly income become ? 6500. What was the monthly income of the person, who is no more?
Options- A. ? 6928
- B. ? 8200
- C. ? 9900
- D. ? 13850 Discuss
- 7. A man divides his total route of journey into three equal parts and decide to travel the three parts with speed of 15 km/h. 10 km/h and 5 km/ h respectively. Find his average speed of during journey.
Options- A. 2.28 km/h
- B. 9 km/h
- C. 14 km/h
- D. 8.18 km /h Discuss
- 8. The average temperature of Delhi for four days in a particular month is 48°C. If the average temperature of second and third days 34°C and the ratio of the temperature of first and fourth days is 9 : 11 then find out the temperature of first and fourth days.
Options- A. 45.5°C, 49.9°C
- B. 32.4°C, 39.8°C
- C. 43.4°C, 68.2°C
- D. 54.4°C, 46.8°C Discuss
- 9. A man spends average of ? 1694. 70 per month for the first 7 month and ? 1810.50 per month for the next 5 months. His monthly salary if he saves ? 3084.60. during the whole year is?
Options- A. ? 2400
- B. ? 3000
- C. ? 1000
- D. ? 2000 Discuss
- 10. In the afternoon, a student read 100 pages at the rate of 60 pages/h. In the evening, when she was tired, she read 100 more pages at the rate of 40 pages/h . What was her average rate of reading in pages per hour?
Options- A. 48
- B. 50
- C. 60
- D. 70 Discuss
Average problems
Search Results
Correct Answer: 45kg
Explanation:
Total weight of 2 men
= 1 x 10 + (42 + 38) = 10 + 80 = 90 kg
? Average weight of 2 men = 90/2 = 45 kg
Correct Answer: 401/3 yr
Explanation:
Total age of 3 woman = 2 X 11 + (32 + 33 + 34)
= 22 + 99 = 121 yr.
? Average age of 3 woman = 121/3 = 401/3 yr
Correct Answer: 50 yr
Explanation:
Total age of 4 member = 25 x 4 = 100 yr
Total age of 5 members including the head
= 5 x (25 + 25 x 20/100)
= 5 x 30 = 150 yr
? Age of the head = 150 - 100 = 50 yr
Correct Answer: 164
Explanation:
Sum of marks of 7 students = Mean x Number of students
= 226 x 7 = 1582
Now, total marks of 6 students = (340 + 180 + 260 + 56 + 275 + 307) = 1418
? Marks obtained by seventh students
= Total marks of seven students - Total marks of the six student
= 1582 - 1418
= 164
Correct Answer: 44
Explanation:
Total number of all students of the class = 30 x 45 = 1350
? New average after adjustment = (1350 - 45 + 15)/30 = 1320/30 = 44
Correct Answer: ? 9900
Explanation:
Monthly income of 4 persons = 7350 x 4 = ? 29400
Monthly income of 3 person (excluding the dead person) = 6500 x 3 = ? 19500
? Monthly income of dead person = 29400 - 19500 = ? 9900
Correct Answer: 8.18 km /h
Explanation:
If three equal distances are covered at different spees of A, B and C km/h, respectively, then average speed during whole journey
= 3ABC/(AB + BC + CA) km/h
? Required average speed
= (3 x 15 x 10 x 5) / (15 x 10 + 10 x 5 + 15 x 5)
= (3 x 15 x 10 x 5)/(150 + 50 + 75)
= (3 x 15 x 10 x 5)/275
= 8.18 km/h
Correct Answer:
Explanation:
Total temperature of first and fourth days= (4 x 48 - 2 x 34)°C
= (192 - 68)°C= 124°C
Now, according to the question
Temperature of the first day = (9/20) x 124 = 55.8°C
Temperature of fourth day = (11/20) x 124 = 68.2°C
Correct Answer: ? 2000
Explanation:
Let the monthly salary of a man = ? N
? The annual salary = ? 12N
According to the question,
Annually spends of a man = 7 x 1694.70 + 5 x 1810.50
= ? 20915.40
? His monthly spends = 20915.40/12 = ? 1742.95
And monthly saving = 3084.60/12 = ? 257.05
? His monthly salary
= 1742.95 + 257.05
= ? 2000
Correct Answer: 48
Explanation:
Required average rate of reading
= 2AB / (A + B) = 2 x 60 x 40 / (60 + 40)
= (2 x 60 x 40)/100 = 48 page/h
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