Multiple choice

John is twice as old as his younger brother Mark. In 10 years, John will be not more than 28 years old. What is the greatest possible value of Mark's current age?

  1. 4

  2. 5

  3. 7

  4. 9

  5. 10
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let Mark's age be x. John's age is 2x. In 10 years, John will be 2x + 10. We have 2x + 10 <= 28, so 2x <= 18, which means x <= 9. The greatest possible value is 9.

AI explanation

Let Mark's current age be x, making John's current age 2x. In 10 years, John will be 2x plus 10 years old, and the condition states this age is not more than 28, so 2x plus 10 is less than or equal to 28. Solving this inequality gives 2x is less than or equal to 18, meaning x is less than or equal to 9. Since Mark's age must be an integer, the greatest possible value for his current age is 9.

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