If V=IR Why are voltage and current interchangeable through a constant resistance
If you re-read your question, then it sort of answer's itself.  Yes...in a pure DC circuit, Ohms Law is King, and so V=I*R.  But you stated they said "I only put 5 Amps through the Circuit....so if they put a constant 5 Amps through the circuit, then the voltage will be the current times the resistance.  Since they didn't state the Resistance, then the value of the Voltage may be a "bunch of Volts"....if the resistance is high enough.  Simply put....under normal everyday simple DC circuits....most people drive them with either a Voltage or Current Source...but typically not both. If they drive the circuit with a Current, then they will see the Voltage go up proportionally.  So I believe maybe they didn't mean they "Put In" both Current and Voltage, but they put in Current and Measured a Bunch of Voltage...or Vice Versa.