Math Problem Statement

answer

The average age of A, B, and C is 24 years. When D joins them, the average age becomes 23 years. A new person, E, whose age is 3 years more than D, replaces A, and the average of B, C, D, and E becomes 26 years. What is the age of A?

Solution

To solve this problem, let's analyze the situation step by step:

  1. Average of A, B, and C is 24 years: A+B+C3=24\frac{A + B + C}{3} = 24 So, A+B+C=72A + B + C = 72

  2. When D joins them, the average age becomes 23 years: A+B+C+D4=23\frac{A + B + C + D}{4} = 23 So, A+B+C+D=92A + B + C + D = 92 Substituting A+B+C=72A + B + C = 72, 72+D=92    D=2072 + D = 92 \implies D = 20

  3. A new person, E, whose age is 3 years more than D (i.e., E=20+3=23E = 20 + 3 = 23), replaces A, and the average of B, C, D, and E becomes 26 years: B+C+D+E4=26\frac{B + C + D + E}{4} = 26 So, B+C+D+E=104B + C + D + E = 104 Substituting D=20D = 20 and E=23E = 23, B+C+20+23=104    B+C=61B + C + 20 + 23 = 104 \implies B + C = 61

  4. Find the age of A: From A+B+C=72A + B + C = 72 and B+C=61B + C = 61, A+61=72    A=11A + 61 = 72 \implies A = 11

The age of A is 11 years.


Do you want further clarification or details on any step?

Here are some related questions for further practice:

  1. If the average age of B and C alone is calculated, what is it?
  2. How would the solution change if E's age was different?
  3. Can you determine the total combined age of all five individuals (A, B, C, D, E)?
  4. What happens to the average if D is replaced by someone with an age of 25?
  5. How would the problem be solved if no replacement occurred but A's age was needed?

Tip: In problems involving averages, always focus on total sums rather than individual averages to simplify calculations.

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Math Problem Analysis

Mathematical Concepts

Averages
Algebra
Basic Arithmetic

Formulas

Average = Sum of terms / Number of terms
Total sum manipulation for averages

Theorems

Basic properties of averages

Suitable Grade Level

Grades 6-8