In a house 5 bulbs of 25 watts each are used for 6 hours a day. Calculate the unit of electricity consumed in a month of 30 days. Also find the total cost if one unit electricity cost 1.50 Rs.

(5 bulbs) x (25 watt/bulb) x (6 hour/day) x (30 day/month) =

(5 x 25 x 6 x 30) watt-hour/month =

22,500 watt-hour/month.

The most common unit of electrical energy used for billing purposes

is the 'kilowatt-hour' = 1,000 watt-hours.

22,500 watt-hour/month = 22.5 kWh/month.

(22.5 kWh/month) x (1.50 Rs/kWh) = 33.75 Rs / month