To convert seconds into minutes you divide the total amount of seconds by 60:
455 seconds รท 60 = 7.583333 minutes.
Then multiply the decimal part by 60 to get the leftover number of seconds:
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It really doesn't matter whether the system is single-phase or three-phase, if you know the power, the rate of supplying energy, then you can work out the amount of energy supplied. If the power (in...