Answer: D ( 17/20)
Step-by-step explanation:
The two choices are:
The ‘standard’ tariff charges = $0.10 per unit
The ‘day/night tariff’ = $0.12 per unit for each unit consumed between 06:00 and 22:00 but only $0.05 for each unit consumed between 22:00 and 06:00
The day time is between 22:00 and 06:00
Time = 22 - 6 = 16 hours
Let assume that the charges are unit per hour.
For standard tariff = (16 × 0.10) + 0.2
Standard tariff = 1.6 + 0.2 = 1.8
For day/night = (16 × 0.12) + 0.2
= 1.92 + 0.2
= 2.12
The proportion will be
1.8/2.12 = 17/20 ( approximately)
