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The blackboard says 0.01, 0.02, 0.03 Then, 1, these 100 numbers, each time arbitrarily erase two of them a, B, and write 2ab-a-b + 1, and ask what is the number left on the blackboard? Why?
zero point five
One of the 100 numbers is 0.5
When a = 0.5, 2ab-a-b + 1 = 2 × 0.5 × b-0.5-b + 1 = 0.5
So when one of the two numbers erased is 0.5, the other no matter what the number is, and then rewrite it with a fixed time of 0.5
So the last one must be 0.5
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