Re: The electricity used by the water heater was measured separately
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10 Oct 2022, 13:09
let per unit Cost be $1 for normal and %0.5 for water heating.
So Water heating Cost: 20% of 800 * 0.5 = $80.
Rest Cost: 80% of 800 * 1 = $640
Total Cost $80 + $640 = $720
So cost of the electricity used by the water heater/ total cost of all the electricity used = \(\frac{$80}{$720}\) = \(\frac{1}{9}\)
Answer: B