Robots Z7
In the school for robots, one class is attended by twenty Robert robots, numbered Robert 1 to Robert 20. There is currently a tense atmosphere in the class, only some robots are talking to each other. Robots with an odd number do not talk with robots with an even number. Among Roberts with odd numbers, only robots that have a number with the same number of digits talk with each other. Roberts
with even numbers talk only with those whose number begins with the same digit. How many pairs of Robert robots can talk with each other mutually?
with even numbers talk only with those whose number begins with the same digit. How many pairs of Robert robots can talk with each other mutually?
Final Answer:
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