Question

Calculate the electricity bill amount for a month of 31 days, if the following devices are used as specified.
(A) 3 bulbs of 40W for 6 hours
(B) 4 tube lights of 50W for 8 hours
(C) A T.V. of 120W for 6 hours
Given the rate of electricity is Rs. $ 2.50 $ per unit.​

Answer 1

Hint We need to calculate the energy used by each device for a month. The total energy consumed by all the devices can be found by adding the energy consumed by each device. The amount is calculated by multiplying the total energy consumed with the rate of electricity per unit.

Complete Step by Step Solution
It has been given that the following devices are used as specified- 3 bulbs of 40W for 6 hours, 4tube lights of 50W for 8 hours and a T.V. of 120W for 6 hours.
Total power the three bulbs consume in a day is given by,
 $ 40W \times 3 = 120Wh $
 $ = 0.12kWh $
Electrical units for one day = $ {{0}}{{.12 \times 6 = 0}}{{.72 units}} $ .
Electrical units for 31 days = $ {{0}}{{.72 \times 31 = 22}}{{.32 units}} $ .
Total power the four tube lights consume in a day is given by,
 $ 50W \times 4 = 200Wh $
 $ = 0.2kWh $
Electrical units for one day = $ {{0}}{{.2 \times 8 = 1}}{{.6 units}} $ .
Electrical units for 31 days = $ {{1}}{{.6 \times 31 = 49}}{{.60 units}} $ .
Total power the television consumes in a day is given by,
 $ 120W6 = 720Wh $
 $ = 0.72kWh $
Electrical units for one day = $ {{0}}{{.72}} \times 6{{ = 4}}{{.32 units}} $ .
Electrical units for 31 days = $ {{4}}{{.32 \times 31 = 133}}{{.92 units}} $ .
Thus, from the above calculations, we can calculate the total electrical units consumed in a month of 31 days.
Total units consumed= Electrical units consumed by bulbs for 31 days + Electrical units consumed by tube lights for 31 days + Electrical units consumed by the television for 31 days.
Thus, the total units consumed= $ 22.32 + 49.60 + 133.92 = 205.84{{units}} $ .
It has been given, that the rate of electricity is Rs. $ 2.50 $ per unit.​
Then the total amount the bill amounts to is given by multiplying the total number of units with the rate of electricity per unit.
Thus, we get the total bill $ 205.84 \times 2.50 = 514.60 $ .
Hence, the electricity bill amount for a month of 31 days amounts to Rs. $ 514.60 $.

Note
To calculate the electric bill, the energy usage of each of the appliances and electronic devices needs to be figured out. In an ideal world, estimating the electricity usage would be as easy as looking at an itemized grocery receipt.
To estimate electricity usage of a particular appliance or electronic device, three figures are needed: the wattage of the appliance, the average number of hours you use it per day, and the price you pay per kilowatt-hour (kWh) of electricity.
To determine the wattage of an appliance, look for a label or metal plate, which is usually in an inconspicuous place like the back or bottom of the appliance or device. If the wattage is listed, it will have a “W” at the end. If a label isn’t found, the appliance’s original documentation can be checked or try searching online for its technical specs.