Math Problem Statement

The ratio of the age of mother and daughter is 2:1. Four years ago, the ratio of son's age to daughter's age was 3:4. The father is 5 years elder than the mother. Two years ago, father's age was 3 times the son's age. What is the daughter's age?

Solution

The problem you're asking is:

  1. The ratio of the ages of the mother and daughter is 2:1.
  2. Four years ago, the ratio of the son's age to the daughter's age was 3:4.
  3. The father is 5 years older than the mother.
  4. Two years ago, the father's age was 3 times the son's age.

You are asked to find the daughter's current age.


Let’s denote:

  • The daughter's current age as xx.
  • The mother's current age as 2x2x (from the given ratio 2:1).

Step 1: Relationship of ages 4 years ago

  • The son's age 4 years ago: S4S - 4.
  • The daughter's age 4 years ago: x4x - 4.
  • According to the problem, S4x4=34\frac{S - 4}{x - 4} = \frac{3}{4}, where SS is the son's current age.

We can express the son's age in terms of the daughter's age by solving this equation.

Step 2: Father's age

  • The father's current age is 2x+52x + 5, since the father is 5 years older than the mother.
  • Two years ago, the father's age was 2x+52=2x+32x + 5 - 2 = 2x + 3.
  • Two years ago, the son's age was S2S - 2, and the problem states that the father's age then was 3 times the son's age: 2x+3=3(S2)2x + 3 = 3(S - 2)

Now, we have two equations:

  1. S4x4=34\frac{S - 4}{x - 4} = \frac{3}{4}
  2. 2x+3=3(S2)2x + 3 = 3(S - 2)

Let’s solve this system of equations to find the daughter’s age.

I'll solve these now.The solution indicates that the daughter's current age is 24 years, and the son's current age is 19 years.

Thus, the answer to the question is:

E. 24 years


Do you have any questions or would you like a detailed explanation of the steps?

Related questions:

  1. How do we derive the equation for the son and daughter's age ratio 4 years ago?
  2. How does the father’s age equation affect the solution?
  3. What would the mother’s and father’s current ages be?
  4. How can we verify the correctness of the solution?
  5. How would the problem change if the age ratios were different?

Tip:

Always set up equations clearly for each condition in the problem before solving the system; it helps avoid confusion in complex word problems.

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Math Problem Analysis

Mathematical Concepts

Age Problems
Algebra
Ratios

Formulas

Age formula: Present age - years ago = past age
Ratio formula: (a - years ago) / (b - years ago) = given ratio

Theorems

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Suitable Grade Level

Grades 8-10