Multiple choice general knowledge math & puzzles

Glenn and Jason each have a collection of tennis balls. Glenn said that if Jason would give him 9 of his balls they would have an equal number; but, if Glenn would give Jason 9 of his balls, Jason would have 4 times as many balls as Glenn. How many balls does Jason have?

  1. 37

  2. 38

  3. 39

  4. 40
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let G be Glenn's balls and J be Jason's balls. From the first condition: G + 9 = J - 9, so J = G + 18. From the second: J + 9 = 4(G - 9). Substituting J: (G + 18) + 9 = 4G - 36, giving G + 27 = 4G - 36, so 3G = 63 and G = 21. Therefore J = 21 + 18 = 39 balls.

AI explanation

Let G = Glenn's balls, J = Jason's balls. If Jason gives Glenn 9: G+9 = J-9, so J = G+18. If Glenn gives Jason 9: J+9 = 4(G-9). Substituting J = G+18 gives G+27 = 4G-36, so 3G = 63, G = 21, and J = 21+18 = 39. So Jason has 39 balls. The other options fail to satisfy both simultaneous equations exactly — only 39 makes both conditions (equal after a 9-ball transfer, and 4x after the reverse transfer) true at once.

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