There are 30 students in a class with an average age of 18 years. If a new boy replaces a boy whose age is 24 years, then the new average becomes 17.5 years. What is the age of the new boy?

9 yrs
12 yrs
7 yrs
8 yrs
11 yrs

LohaHridoy

5 views

2025-01-04 04:42

1 Answers

AhmedNazir

Option 1 : 9 yrs

Given:

Average age of 30 students = 18 years

Replaced boy's age = 24 years

New average = 17.5 years

Formula used:

Average= sum of observations/total number of observations

Calculation:

Total age of class = 18 × 30 = 540 yrs

Total age after new boy joined = 17.5 × 30 = 525 yrs

Difference = 540 - 525 = 15 years

This difference is due to the age difference between replaced students,

New boy's age = 24 - 15 = 9 yrs

∴ The age is 9 years.

Alternate Method

Reduction in average age = 5 years

total reduction = 30 × .5 = 15 years

This reduction is due the replacement

New boy's age = 24 - 15 = 9 yrs

∴ The age is 9 years.

5 views Answered 2022-09-04 04:29

Related Questions

There are 30 students in a class. The average age of the first 10 students is 12.5 years. The average age of the remaining 20 students is 13.1 years. The average age (in years) of the students of the whole class is:?

1 Answers 4 Views

The average marks obtained by 42 students of class A is 79 whereas, the average marks of 38 students of class B is 76. If marks of 5 students are removed who got minimum marks from class A, the average marks of class A is increased by 3 marks, then find the new average marks of class A and B.?

1 Answers 4 Views

Average age of P, Q and R is 90 years. When S joins them the average age becomes 86 years. A new person T whose age is 6 years more than S, replaces P and the average of Q, R, S and T becomes 84 years. What is the age of P?

1 Answers 6 Views

The average age of 20 students of a class is 12 years. Now a student whose age is 15 years leaves the class, and another student whose age is 13 years enters the class. Find the new average age of the class (in years).?

1 Answers 4 Views

A class has 20 boys and 20 girls. The average age of girls in the class is 16 years and the average age of boys in the class is 17 years. One girl and one boy leave the class and the average age of the girls reduced by 1 year and that of boys reduced by 2 years. Find the new average age of the whole class.?

1 Answers 9 Views

There are 120 students in a class. The number of boys is 40% more than the number of girls in the class. The average age of boys in the class is 24 years and the average age of the whole class is 30 years. Then, what is the average age of girls in the class?

1 Answers 6 Views

Quantity I: The average age of a cricket team of 11 players is x years. After three years, four players leave the team and four new players join in place of them then the current average age becomes (x + 2) years. The current average age of the players who left the team was 18 years then find the average of the current age of the 4 new joiners Quantity II: In a group of 6 students, the average age of the 5 youngest students is 12 years and the average age of the 5 oldest students is 15 years. What is the average age of all the students (it is given that the age of them is in arithmetic progression)?

1 Answers 5 Views

Questions below followed by three quantities. Find the relationship between them. Quantity I: In a class with a certain number of students if a teacher weighing 78 kg is added, then average weight of class is increased by 2 kg. If one more teacher weighing 66 kg is added, then the average weight of the class increases by 3.5 kg over the original average. What is the original average weight (in kg) of the class Quantity II: The average age of 16 students and their teacher's age is 16 years. If the teacher's age is excluded, the average reduces by 2. What is the teacher's age Quantity III: Average weight of three friends A, B and C is 46 kg. Another person D joins the group and now the average is 45 kg. If another person E whose weight is 6 kg more than D, joins the group replacing A, then average weight of B, C, D and E becomes 47 kg. What is the weight of A (in kg)?

1 Answers 9 Views

The average marks of a class of 30 students are 52. One student whose marks are 82 left the class and two new students joined the class. The average of the class remains the same and the difference between the marks of new students is 4. What will be the marks of the student who scored greater marks between the two new students?

1 Answers 4 Views

A group of three friends, K, L and M, are sitting in a café. Their average age is 24 years. Another friend ‘N’ joins the group and the new average age of the group becomes 23 years. If another friend ‘R’, whose age is 2 years more than that of ‘N’, replace ‘K’, then the average age of L, M, N and R becomes 22.5 years. What is the age of K?

1 Answers 4 Views

এক্সাম দিয়ে মেধা যাচাই করুন

Job Preparation (1125)

Admission (754)

এসএসসি (10)

এইচএসসি (5)