Question

Calculate the electricity bill amount for a month of 30 days, if the following devices are used as specified: a) 3 bulbs of 40 W for 6 hours (b) 4 tube lights of 50 W for 6 hours. c) A refrigerator of 320 W for 24 hours. Given the rate of electricity is Rs 2.50 per unit.
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Answer 1

Answer:

Given :

• 2 bulbs of 40 W runs for 6hours
• 2 tubelights of 50 W runs for 8 hours
• a TV of 120 W runs for 6 hours.
• cost of electricity is Rs. 2.50 per unit.

To Find :

• The electricity bill amount for a month of 30days

Solution :

Electrical energy consumed by two bulbs in 30 days = 2×40×6×30

                                                                                        = 14400 watt.hour

                                                                                       = 14.4 KWH

Electrical energy consumed by two tubelights in 30 days = 2×50×8×30

                                                                                             = 24000 watt.hr

                                                                                            = 24 KWH        

Electrical energy consumed by a TV in 30 days = 120×6×30

                                                                               = 21600 watt.hr

                                                                              = 21.6 KWH

As we know, 1 KWH = 1 unit, and the cost per unit is given Rs. 2.50

The total electricity bill of one month = (14.4 + 24 + 21.6) × 2.50

                                                             = Rs. 150

Therefore, The total electricity bill of one month is Rs. 150

Answer 2

Answer:

Step 1: Calculate individual units consumed by each appliances in a day.

a) 4 bulbs of 60W each for 6 hours a day.

Power of one bulb, P

1

=60W=0.06kW

Unit consumed in one day by one bulb, =0.06×6=0.36kWh

Unit consumed in one day by four such bulb, =0.36×4=01.44kWh

b) 3 tube lights of 40W each for 8 hours a day.

Power of one tube light, P

2

=40W=0.04kW

Unit consumed in one day by one tube light =0.04×8=0.32kWh

Unit consumed in one day by three such tube light =0.32×3=0.96kWh

c) A refrigerator of 300W for 24 hours a day.

Power of refrigerator, P

3

=300W=0.3kW

Unit consumed by refrigerator in one day =0.3×24=7.2kWh

d) An electric mixer of 750W for 1 hour in a day.

Power of electric mixer, P

4

=750W=0.75kW

Units consumed by electric mixer in one day is =0.75×1=0.75kWh

e) A T.V. of 100W for 6 hours a day.

Power of T.V., P

5

=100W=0.1kW

Unit consumed by T.V. in one day is =0.1×6=0.6kWh

• Step 2: Calculate total units consumed by all appliances in one month.
• Total unit consumed in one day is, =1.44+0.96+7.2+0.75+0.6=10.95kWh
• Thus,
• Total units consumed in one month is, 30×10.95=328.5kWh
• Step 3: Calculate Cost of units of one month.
• It is given that cost of one unit is 3Rs.. Then cost of 328.5 units (or kWh) will be,
• cost=3×328.5=985.5Rs.
• Thus, electricity bill amount for a month of 30 days will be, 985.5Rs.