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Question

If 5 times A's age is added to B's age, the sum is 95 years. If 2.2 times B's age is added to A's age, the sum is 63 years. What is B's age (in years)?

The correct answer is
22

Understanding the Age Word Problem

This problem involves finding the ages of two individuals, A and B, based on relationships given between their ages. We need to set up and solve a system of linear equations to find B's age.

Setting Up the Equations

Let's denote the age of A as $A$ and the age of B as $B$. We can translate the information given in the question into two mathematical equations:

  • "If 5 times A's age is added to B's age, the sum is 95 years." This can be written as:
    $5A + B = 95$ (Equation 1)
  • "If 2.2 times B's age is added to A's age, the sum is 63 years." This can be written as:
    $A + 2.2B = 63$ (Equation 2)

Solving for B's Age Step-by-Step

We have a system of two linear equations with two variables:

  1. $5A + B = 95$
  2. $A + 2.2B = 63$

We can use the substitution method to solve this system. First, let's isolate $B$ in Equation 1:

From Equation 1: $B = 95 - 5A$

Now, substitute this expression for $B$ into Equation 2:

$A + 2.2(95 - 5A) = 63$

Distribute the 2.2:

$A + (2.2 \times 95) - (2.2 \times 5A) = 63$

$A + 209 - 11A = 63$

Combine the terms with $A$:

$209 - 10A = 63$

Now, we need to solve for $A$. Subtract 209 from both sides:

$-10A = 63 - 209$

$-10A = -146$

Divide by -10:

$A = \frac{-146}{-10}$

$A = 14.6$

So, A's age is 14.6 years. Now we can find B's age using the expression we found earlier ($B = 95 - 5A$):

$B = 95 - 5(14.6)$

$B = 95 - 73$

$B = 22$

Verification

Let's check if these ages satisfy the original conditions:

  • Condition 1: $5A + B = 5(14.6) + 22 = 73 + 22 = 95$. (Matches)
  • Condition 2: $A + 2.2B = 14.6 + 2.2(22) = 14.6 + 48.4 = 63$. (Matches)

Both conditions are satisfied.

Conclusion

Based on the calculations, B's age is 22 years.

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Important Questions from Linear Equation in 2 or more Variables

  1. Six years ago, the ratio of ages of A to B was 7 ∶ 5. After 4 years from now, the ratio of their ages will be 11 ∶ 9. What is A’s age at present?

  2. 7p - [3q - {8p - (4q - 10p)}] = ?

  3. Surya is 25 years older than his son. In 5 years, he will be twice as old as his son. What will be Surya’s age after 3 years?

  4. The difference between the ages of two sisters is 2 years when father’s age is 52. Father is elder by 2 years to mother. Elder sister’s age is half of mother’s age. Find the age of younger sister?

  5. The sum of the digits of a 2 digit number is 9, When 27 is added to the number, the digits get interchanged. Find the number.

    A. 45

    B. 36

    C. 18

    D. 27
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