Reasoning : Logical Reasoning & Analytical Ability

Q 109 / 325

UPSC CSE Prelims 2021

X said Y, “At the time of your birth I was twice as old as you are at present.” If the present age of X is 42 years, then consider the following statements:

  1. 8 years ago, the age of X was five times the age of Y.
  2. After 14 years, the age of X would be two times the age of Y.

Which of the above statements is/are correct?

EXPLANATION

Correct Option (B)

Let the present age of Y be 't' years. The present age of X is given as 42 years.

According to the statement, "At the time of your birth I was twice as old as you are at present."

  • The age of X at the time of Y's birth can be expressed as the present age of X minus the present age of Y: 42−t.
  • This age was twice Y's present age: 2t.
  • Equating these two expressions: 42−t=2t.
  • Solving for t: 42=3t⇒t=423=14 years.
  • Therefore, the present age of Y is 14 years.

Evaluating Statement 2: "After 14 years, the age of X would be two times the age of Y."

  • Age of X after 14 years = 42+14=56 years.
  • Age of Y after 14 years = 14+14=28 years.
  • Comparing their ages: 56=2×28. This relationship holds true.
  • Thus, Statement 2 is correct.

Incorrect Options:

Evaluating Statement 1: "8 years ago, the age of X was five times the age of Y."

  • Age of X eight years ago = 42−8=34 years.
  • Age of Y eight years ago = 14−8=6 years.
  • Comparing their ages: 34≠5×6, as 5×6=30.
  • Thus, Statement 1 is incorrect because 34 is not equal to 30.