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A is 12 years older than B. 4 years ago, A was twice as old as B. Find the present ages of A and B. - Mathematics

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Question

A is 12 years older than B. 4 years ago, A was twice as old as B. Find the present ages of A and B.

Sum
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Solution

Given:

  • A is 12 years older than B.
  • 4 years ago, A was twice as old as B.

Step-wise calculation:

1. Let B’s present age be (x) years.

2. Therefore, A's present age is (x + 12) years.

3. Four years ago:

B’s age was (x – 4).

A’s age was (x + 12 – 4 = x + 8).

4. According to the problem,

4 years ago A was twice as old as B: 

x + 8 = 2(x – 4)

5. Simplify the equation:

x + 8 = 2x – 8 

8 + 8 = 2x – x 

16 = x

6. So, B is 16 years old.

7. Then A’s present age is x + 12 = 16 + 12 = 28.

Present age of A = 28 years.

Present age of B = 16 years.

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Chapter 5: Simultaneous Linear Equations - Exercise 5E [Page 121]

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Nootan Mathematics [English] Class 9 ICSE
Chapter 5 Simultaneous Linear Equations
Exercise 5E | Q 12. | Page 121
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