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[This is from one of my friends, a year ago]

We have 6 weights: 2 red, 2 black, 2 blue. Of each color, there is one that's 100g and one that's 101g. How can you identify which ones are 101g, in two measurements, with a one-armed scale?

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  • Name 6 weights as R1, R2, K1, K2, B1, B2.
  • Meansure R1 + K1 + B1
    • R1 + K1 + B1 = 300g: R2, K2, B2 are 101g
    • R1 + K1 + B1 = 301g:
      • Meansure R1 + K2
        • R1 + K2 = 200g: R2, K1, B2 are 101g
        • R1 + K2 = 201g: R2, K2, B1 are 101g
        • R1 + K2 = 202g: R1, K2, B2 are 101g
    • R1 + K1 + B1 = 302g:
      • Meansure R1 + K2
        • R1 + K2 = 200g: R2, K1, B1 are 101g
        • R1 + K2 = 201g: R1, K1, B2 are 101g
        • R1 + K2 = 202g: R1, K2, B1 are 101g
    • R1 + K1 + B1 = 303g: R1, K1, B1 are 101g

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