Multiple choice

Twelve years ago, Mark was twice as old as his brother Jones. Also, twelve years from now, he will be 1.2 times as old as Jones. What is the age of Jones at present (in years)?

  1. 6

  2. 12

  3. 18

  4. 30

  5. 36
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let M and J be current ages. 12 years ago: (M-12) = 2(J-12) => M = 2J - 12. In 12 years: (M+12) = 1.2(J+12). Substituting M: (2J - 12 + 12) = 1.2J + 14.4 => 2J = 1.2J + 14.4 => 0.8J = 14.4 => J = 18.

AI explanation

Let the present ages of Mark and Jones be M and J. Twelve years ago, M minus 12 equals 2 multiplied by (J minus 12), which simplifies to M = 2J minus 12. Twelve years from now, M + 12 = 1.2 times (J + 12), which simplifies to M = 1.2J + 2.4. Equating the two expressions for M gives 2J minus 12 = 1.2J + 2.4, meaning Jones is 18 years old today.

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