Multiple choice general knowledge math & puzzles

Five years ago, John’s age was half of the age he will be in 8 years. How old is he now?

  1. 8

  2. 4

  3. 14

  4. 18

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let John's current age be x. Five years ago he was (x-5). In 8 years he will be (x+8). The equation is (x-5) = (x+8)/2. Solving: 2x-10 = x+8, so x = 18. Checking: five years ago he was 13, in 8 years he'll be 26, and 13 is half of 26.

AI explanation

To solve this problem, let's first set up an equation based on the given information.

Let's assume John's current age is represented by "x".

Five years ago, John's age was "x - 5". In 8 years, John's age will be "x + 8".

According to the given information, John's age five years ago was half of the age he will be in 8 years. Mathematically, we can write this as:

x - 5 = (1/2)(x + 8)

To solve this equation, we can multiply both sides by 2 to eliminate the fraction:

2(x - 5) = x + 8

Expanding the equation:

2x - 10 = x + 8

Now, let's solve for x:

2x - x = 8 + 10 x = 18

Therefore, John is currently 18 years old.

The correct answer is option D.