Average
- The average of marks of 28 students in Mathematics was 50; 8 students left the school, then this average increased by 5. What is the average of marks obtained by the students who left the school ?
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The average of marks of 28 students in Mathematics = 50
Total marks of 28 students = 28 × 50 = 1400
When 8 students left , The average of marks of 20 students = 55
Total marks of 20 students = 20 × 55 = 1100Correct Option: B
The average of marks of 28 students in Mathematics = 50
Total marks of 28 students = 28 × 50 = 1400
When 8 students left , The average of marks of 20 students = 55
Total marks of 20 students = 20 × 55 = 1100
∴ Total marks of 8 students = 1400 – 1100 = 300
∴ Average = 300 ÷ 8 = 37.5
- The average age of 14 girls and their teacher’s age is 15 years. If the teacher’s age is excluded, the average reduces by 1. What is the teacher’s age?
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According to question ,
Total age of 14 girls + 1 teacher = 15 × 15 = 225 yrs.
Average age of 14 girls = 14 yrs.
∴ Total age of 14 girls = 14 × 14 = 196 yrs.Correct Option: D
According to question ,
Total age of 14 girls + 1 teacher = 15 × 15 = 225 yrs.
Average age of 14 girls = 14 yrs.
∴ Total age of 14 girls = 14 × 14 = 196 yrs.
∴ Teacher’s age = 225 – 196 = 29 yrs.
- The frequency distribution data is given below. If the average age is 17 years, the value of m is
Age (in years) : 8 20 26 29 Number of people : 3 2 m 1
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As per the given details in question , we have
Required average = 8 × 3 + 20 × 2 + 26 × m + 29 × 1 3 + 2 m + 1 ⇒ 17 = 24 + 40 + 26m + 29 6 + m
⇒ 17 (6 + m) = 93 + 26 m
⇒ 102 + 17m = 93 + 26m
Correct Option: A
As per the given details in question , we have
Required average = 8 × 3 + 20 × 2 + 26 × m + 29 × 1 3 + 2 m + 1 ⇒ 17 = 24 + 40 + 26m + 29 6 + m
⇒ 17 (6 + m) = 93 + 26 m
⇒ 102 + 17m = 93 + 26m
⇒ 26m – 17m = 102 - 93
⇒ 9m = 9
⇒ m = 1
- Three years ago, the average age of a family of 5 members was 17 years. A baby having been born the average age of the family is the same today. The present age of the baby (in years) is
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Here , Three years ago, the average age of 5 members = 17 years
Three years ago, Total age of the family = 17 × 5 = 85 years
Total age of 5 member family today = 85 + 15 = 100 years
Born on baby , the average age of 6 members = 17 years
Total age of the family with child today = 17 × 6 = 102 yearsCorrect Option: A
Here , Three years ago, the average age of 5 members = 17 years
Three years ago, Total age of the family = 17 × 5 = 85 years
Total age of 5 member family today = 85 + 15 = 100 years
Born on baby , the average age of 6 members = 17 years
Total age of the family with child today = 17 × 6 = 102 years
Age of baby = 102 – 100 = 2 years
- 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 is
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According to question ,
Increase in ages of five members in 3 years = (3 × 5) years = 15 years
As average age remains same,Correct Option: D
According to question ,
Increase in ages of five members in 3 years = (3 × 5) years = 15 years
As average age remains same,
∴ Required difference = 15 years
