Question

Calculate the electricity bill amount for a month of April, if 4 bulbs of 40 W for 5 h, 4 tubelights of 60 W for 5 h, a TV of 100 W for 6 h, a washing machine of 400 W for 3 h are used per day. The cost per unit is Rs 1.80.

Answer 1

Electric energy consumed per day by 4 bulbs = 4 x 40 x 5 = 800 Wh

Electric energy consumed per day by 4 lights = 4 x 60 x 5 = 1200 Wh

Electric energy consumed per day by TV = 100 x 6 = 600 Wh

Electric energy consumed per day by washing machine = 400 x 3 = 1200 Wh

∴ Total electric energy consumed by all electric appliances

= (800 + 1200 + 600 + 1200) Wh

= 3800 Wh

= 3.8 kWh

= 3.8 units

Total electric energy consumed in the month of April (30 days) = 3.8 x 30 = 114 units

Cost of one unit = Rs. 1.80

Cost of 114 units = 114 x Rs. 1.80 = Rs. 205.20

∴ Electricity bill amount = Rs. 205.20

Answer 2

Energy used by light bulbs in one day= 40w x 5 x 4 = 0.8 kwh
Energy used by tube lights in one day= 60w x 5 x 4 = 1.2 kwh
Energy used by TV in one day= 100w x 6 = 0.6 kwh
Energy used by washing machine in one day = 400w x 3 = 1.2 kwh
So, total energy used in one day= 0.8 + 0.6 + 1.2 + 1.2 = 3.8 kwh

Total energy used in 30 days (April has 30 days) = 3.8 x 30 = 114 kwh
Now, 1 kwh = 1 unit
And, Cost per unit = Rs.1.8
Therefore, the bill for the entire month = 114 x 1.8= Rs. 205.2

Answer 3

Energy used by light bulbs in one day = 40w*5*4 = 0.8 kwh

Energy used by tube lights in one day = 60w*5*4 = 1.2 kwh

Energy used by TV in one day = 100 w*6 = 0.6kwh

Energy used by washing machine in one day = 400w*3 = 1.2 kwh

Total energy used in one day = 0.8 + 0.6 + 1.2 + 1.2 = 3.8 kwh

Total energy used in 30 days ( because April has 30 days) = 3.8 x 30 = 114 kwh

1 kwh = 1 unit  
Cost per unit = Rs 1.8  

So the bill for the entire month is 205.2 (114 x 1.8)