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jmc

number theory senior

Problem

Ed and Sue bike at equal and constant rates. Similarly, they jog at equal and constant rates, and they swim at equal and constant rates. Ed covers kilometers after biking for hours, jogging for hours, and swimming for hours, while Sue covers kilometers after jogging for hours, swimming for hours, and biking for hours. Their biking, jogging, and swimming rates are all whole numbers of kilometers per hour. Find the sum of the squares of Ed's biking, jogging, and swimming rates.
Solution
Let the biking rate be , swimming rate be , jogging rate be , all in km/h. We have . Subtracting the second from twice the first gives . Mod 4, we need . Thus, . and give non-integral , but gives . Thus, our answer is .
Final answer
314