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Question

Ram’s father is twice as old as Ram is. Eight years ago, the age of Ram’s father was 2.5 times his age. What is Ram’s current age?

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is

24 years

Understanding the Age Word Problem

This problem involves finding the current age of Ram based on two pieces of information relating his age and his father's age at two different points in time: the present and eight years ago. Age problems are often solved by setting up equations based on the given relationships and then solving those equations.

Setting up the Equations for Age Calculation

Let's use variables to represent the current ages:

  • Let Ram's current age be $R$ years.
  • Let Ram's father's current age be $F$ years.

Now, we translate the given information into mathematical equations:

  1. "Ram’s father is twice as old as Ram is."

    This gives us the first equation:

    $$F = 2R \quad (Equation \; 1)$$

  2. "Eight years ago, the age of Ram’s father was 2.5 times his age."

    First, let's determine their ages eight years ago:

    • Ram's age 8 years ago was $R - 8$ years.
    • Ram's father's age 8 years ago was $F - 8$ years.

    Now, set up the relationship given for their ages eight years ago:

    $$F - 8 = 2.5 \times (R - 8) \quad (Equation \; 2)$$

Solving for Ram's Current Age

We now have a system of two linear equations with two variables ($R$ and $F$). We can use substitution to solve for $R$.

Substitute the expression for $F$ from Equation 1 ($F = 2R$) into Equation 2:

$$ (2R) - 8 = 2.5 \times (R - 8) $$

Now, let's solve this equation for $R$ step-by-step:

Expand the right side of the equation:

$$ 2R - 8 = 2.5R - 2.5 \times 8 $$

Calculate $2.5 \times 8$:

$$ 2.5 \times 8 = \left(\frac{5}{2}\right) \times 8 = 5 \times 4 = 20 $$

Substitute this value back into the equation:

$$ 2R - 8 = 2.5R - 20 $$

Gather the terms with $R$ on one side and the constant terms on the other side. Subtract $2R$ from both sides:

$$ -8 = 2.5R - 2R - 20 $$

$$ -8 = 0.5R - 20 $$

Add 20 to both sides:

$$ -8 + 20 = 0.5R $$

$$ 12 = 0.5R $$

To find $R$, divide both sides by 0.5 (which is the same as multiplying by 2):

$$ R = \frac{12}{0.5} $$

$$ R = 12 \times 2 $$

$$ R = 24 $$

So, Ram's current age is 24 years.

Verification of the Age Solution

Let's check if this age satisfies the original conditions:

  • Ram's current age $R = 24$ years.
  • Father's current age $F = 2R = 2 \times 24 = 48$ years.

Now check the condition for eight years ago:

  • Ram's age 8 years ago = $24 - 8 = 16$ years.
  • Father's age 8 years ago = $48 - 8 = 40$ years.

Was the father's age 2.5 times Ram's age 8 years ago?

Calculate $2.5 \times (\text{Ram's age 8 years ago})$:

$$ 2.5 \times 16 = \left(\frac{5}{2}\right) \times 16 = 5 \times 8 = 40 $$

The father's age 8 years ago was indeed 40 years, which matches $2.5$ times Ram's age (16 years) at that time. The solution is verified.

Summary of Ages
Person Current Age Age 8 Years Ago
Ram 24 $24 - 8 = 16$
Father 48 $48 - 8 = 40$

The calculated current age of Ram is 24 years.

Revision Table: Key Concepts in Age Problems

Age Problem Formulas and Concepts
Concept Explanation Mathematical Representation
Present Age The age right now. Variable (e.g., $x$, $y$)
Age in the Future Age after $t$ years. Present Age $+ t$
Age in the Past Age $t$ years ago. Present Age $- t$
Relationship between Ages How one person's age relates to another's (e.g., twice as old, 5 years older). Equation (e.g., $y = 2x$, $y = x + 5$)

Additional Information on Solving Algebraic Word Problems

Age problems are a common type of word problem that can be solved using algebra. Here are some general tips for approaching such problems:

  • Read Carefully: Understand the relationships and the different points in time mentioned in the problem.
  • Define Variables: Assign variables to the unknown quantities, usually the current ages.
  • Formulate Equations: Translate each statement in the problem into a mathematical equation using the defined variables. Pay attention to phrases like "is", "was", "will be", "times", "older than", "younger than".
  • Solve the System: Use algebraic methods (like substitution or elimination) to solve the system of equations you created.
  • Answer the Question: Make sure your final answer directly addresses what the question is asking for.
  • Verify Your Answer: Plug your solution back into the original word problem (not just the equations) to ensure it makes sense and satisfies all conditions.

Practicing different types of word problems, including age problems, helps in developing skills to translate verbal information into mathematical models.

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Similar Questions

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  2. Three years from now Dhahiri’s age will be eight years less than twice Eunice’s age. The sum of their present ages is 61 years. What is Dhahiri’s present age?

  3. The sum of the present ages of two cousins is 46 years. Eight years ago, the elder one was twice as old as the younger one. What is the present age of the elder cousin?

  4. Present ages of Sai and Satheesh are in the ratio of 5 : 4 respectively. Three years hence, the ratio of their ages will become 11 : 9 respectively. What is Satheesh’s present age in years?

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Important Questions from Age

  1. The ages of two persons P and Q are in the ratio 5 : 7. Eight years ago, the ratio of P and Q was 7 : 13. The present ages of P and Q, respectively, are:

  2. One year ago, the ratio of the ages of A and B was 4 : 3. The ratio of their ages, after 7 years from now, will be 9 : 7. What is the present age (in years) of B?

  3. In 8 years, Subhash will be 3 times as old as he is now. After how many years will Subhash be 5 times as old as he is now?

  4. The average ages of parents and two children are 30 years and 8 years respectively. The average age of the family is

    A. 16 years

    B. 19 years

    C. 18 years

    D. 17 years

  5. A father is presently 3 times his daughter’s age. After 10 years he will be twice as old as her. Find the daughter’s present age.

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