Question

a 100 watt bulb is used for 10 hours everyday find the cost of electricity if the rate is rs 4/unit for 30 days.

Answer 1

100 W = 0.1 kWh

for 10 hours

=> 0.1 * 10 = 1 kWh per day

for 30 days it should be

1 * 30 = 30 kWh

rate = 4/unit

=> 30 * 4

=> 120 Rs

Answer 2

Power consumed=power in watt × hours ÷1000
w=100 h=10×30=300
=100×300
----------------
1000
=30000
-------------- = 30 units
1000
power consumed in thirty days=30 units
cost of electricity= 30×4=120Rs....

hope it helps you dear......