I am a fraction. If you add 1 to my numerator, I reduce to 1/2. If you add 1 to my denominator instead, I reduce to 1/3. What fraction am I?
3/7
For 3/7, adding 1 to the numerator gives 4/7? Wait, let's check: (3+1)/7 = 4/7 (not 1/2). Let's re-evaluate: Fraction is 3/7? No, let's test 5/11: (5+1)/11 = 6/11. Let's test 3/7: numerator 3, denominator 7. (3+1)/7 = 4/7. Let's look at correct math: (x+1)/y = 1/2 => 2x + 2 = y. x/(y+1) = 1/3 => 3x = y + 1 => y = 3x - 1. Substitute: 2x + 2 = 3x - 1 => x = 3. y = 2(3) + 2 = 8. Fraction is 3/8. Let's check 3/8: (3+1)/8 = 4/8 = 1/2. 3/(8+1) = 3/9 = 1/3. The answer is 3/8.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Hard. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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