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Question: A household uses the following electric appliance: 1) Refrigerator of rating \(400W\) for \(10\) ...

A household uses the following electric appliance:

  1. Refrigerator of rating 400W400W for 1010 hours daily
  2. 22 Electric Fans of rating 80W80W each for 1212 hours daily
  3. 66 electric tubes of rating 18W18W each for 66 hours daily
    Calculate the electricity bill of the household for the month of June if the cost per unit electric energy is Rs 3.003.00.
Explanation

Solution

Hint: - Convert the rating of each appliance into SI units and then multiply it by the number of hours the particular appliance is run daily. This gives the units consumed by the appliance in one day. If there are more than 1 appliance of the same kind, multiply it accordingly. Add all such values of all the appliances. This will give the total units consumed in one day. Now, the months of June consist of 3030 days. So, multiply the units consumed in a day by 30 to get units consumed in June. Multiply this answer by the rate of each unit of electric energy as given in the question to find out the electricity bill for June.

Step-by-step solution:
First, convert the rating of each appliance into the SI unit that is KWKW.
We know that, 1W=10−3KW1W = {10^{ - 3}}KW
Rating for refrigerator = 400W=400×10−3=0.4KW400W = 400 \times {10^{ - 3}} = 0.4KW
Rating for each fan = 80W=80×10−3=0.08KW80W = 80 \times {10^{ - 3}} = 0.08KW
Rating for each electric tube = 18W=18×10−3=0.018KW18W = 18 \times {10^{ - 3}} = 0.018KW
Now, multiply each rating with the number of hours they are used every day.
We get,
For refrigerator, 0.4×10KWh0.4 \times 10KWh
For each fan, 0.08×12KWh0.08 \times 12KWh
For each electric tube, 0.018×6KWh0.018 \times 6KWh
Now, multiply these values with the number of that kind of appliances respectively, we get,
For refrigerator, 0.4×10×1=4KWh0.4 \times 10 \times 1 = 4KWh
For fan, 0.08×12×2=19.2KWh0.08 \times 12 \times 2 = 19.2KWh
For the electric tube, 0.018×6×6=0.648KWh0.018 \times 6 \times 6 = 0.648KWh
Add these values to get units consumed in a day.
We get, (4+19.2+0.648)KWh(4 + 19.2 + 0.648)KWh = 23.848KWh23.848KWh
Since June has 3030 days, multiply this by 3030 to get the number of units consumed in June
⇒ 23.848KWh23.848KWh × 3030 = 715.44units715.44units
Since the rate of each unit is Rs.3.00Rs.3.00, we multiply the above value by 3.003.00 to get the final answer.
715.44×3715.44 \times 3 = Rs.2146.32Rs.2146.32

Note: Convert into SI units before starting the question. Don’t forget to multiply by the number of appliances otherwise, it will be the value of only a single appliance. And it is important to know that June has 30 days, so students should not be confused in that part.