Question

The average consumption of electricity in a house was 18 units/day for the first x days of August. For the next 3x days the average consumption was 16 units/day. For the next 3x days the average consumption was 1.5 units/day more than the average consumption of the first 4x days and the total consumption of the last 3 days of the month was 78 units. Find the average consumption per day of August.
1. 16 units/day
2. 22 units/day
3. 20 units/day
4. 18 units/day
5. 17 units/day

Answer 1

Correct Answer - Option 4 : 18 units/day

Formula used:

Average = sum of observations/total number of observations

Calculation:

Total days in august = 31

So, 31 = x + 3x + 3x + 3

⇒ x = 4 days

Total consumption for 4 days = 18 × 4 = 72 units

Total consumption for next 12 days = 16 × 12 = 192 units

Average consumption of 4x days = (192 + 72)/16 = 16.5 units/day

Average consumption of next 12 days = 16.5 + 1.5 = 18 units/day

Total consumption for next 12 days = 18 × 12 = 216 units

Total consumption = 192 + 72 + 216 + 78 = 558 units

∴ Average consumption = 558/31 = 18 units/day

∴ The average consumption was 18 units/day.