Question

Shanika and Vanesa are comparing their electric bills for the past month. Shanika is on a standard use plan and Vanesa is on an interval use plan. Each person’s usage is listed on the chart below:

Standard Use Plan
Interval Use Plan
7.5 cents/kWh for the first 400 kWh
10 cents/kWh for the next 400 kWh
12.5 cents/kWh for anything over 800 kWh
On-peak hours - 15 cents/kWh
Off-peak hours - 3 cents/kWh

Both women use 1,325 kWh for the given 30 day period. Vanesa uses 500 kWh during on-peak hours and 825 during off-peak hours. Which person ends up paying more for their utilities? How much more?
a.
Vanesa pays $35.88 more than Shanika.
b.
Vanesa pays $99.75 more than Shanika.
c.
Shanika pays $35.88 more than Vanesa.
d.
Shanika pays $99.75 more than Vanesa

Answer 1

Calculate each bill.

Shanika (standard plan, 1,325 kWh):
- First 400 kWh at $0.075 = 400·0.075 = $30.00
- Next 400 kWh at $0.10 = 400·0.10 = $40.00
- Remaining 525 kWh at $0.125 = 525·0.125 = $65.625 → $65.63 (rounded)
Total = $30.00 + $40.00 + $65.63 = $135.63

Vanesa (interval plan):
- On-peak 500 kWh at $0.15 = 500·0.15 = $75.00
- Off-peak 825 kWh at $0.03 = 825·0.03 = $24.75
Total = $75.00 + $24.75 = $99.75

Difference: $135.63 − $99.75 = $35.88

Answer: c. Shanika pays $35.88 more than Vanesa.