Multiple choice

Jack's present age is two fifths of his grandfather's age. After 16 years, Jack's age will be half of his grandfather's age. What is the present age of Jack?

  1. 31 years

  2. 32 years

  3. 34 years

  4. 41 years

  5. 80 years
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let J be Jack's age and G be grandfather's age. J = 2/5 * G. (J+16) = 1/2 * (G+16). Substitute J: 2/5*G + 16 = 1/2*G + 8. 8 = 1/2*G - 2/5*G = 1/10*G. G = 80. J = 2/5 * 80 = 32.

AI explanation

Let Jack's present age be J and his grandfather's age be G, so J = (2/5)G. After 16 years, J + 16 = (1/2)(G + 16), which simplifies to 2J + 32 = G + 16. Substituting (2/5)G for J gives (4/5)G + 32 = G + 16, resulting in G = 80. Jack's present age is two fifths of 80, which is 32 years.

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