How much money can be saved per month by using a compact fluorescent lamp of 15 W in place of an incandescent bulb of 100 W if they are used 8 hours per day for 30 days? (Take the cost of one unit of electrical energy as Rs. 2)

Explanation

(i) One commercial unit of electrical energy is equal to 1 kilowatt hour.
The number of units of electrical energy used in a month can be calculated as `E=pxxtxx30`.
where 't' is in hours.
The cost of the electrical energy can be determined from the equation, cost = energy `xx` cost per unit.
Compare the cost of electrical energy in both the cases.
(ii) Rs. 40.80