Two electric bulbs rated 50 W and 40 W respectively are used 5 hours per day for 20 days . If the cost of a unit is Rs . 4.00, find the cost of the energy used.

An electric bulb rated 60 W and 40 W respectively are used 5 hours per day for 20 days . If the cost of a unit is Rs. 4.00, find the cost of the energy used.

Two electric bulbs rated 60 W and 40 W respectively are used 5 hours per day for 20 days. If the cost of a unit is ₹ 4.00 , find the cost of the energy used.

If 8 pens cost Rs. w, find the cost of 5 such pens.

An electric appliance rated 400 W is used 5 hours per day in the month o June. If the cost of a unit is ₹3.00 , find the energy bill for June.

An electric geyser rated 500 W operates one hour/day. If the cost of unit is 3.00, find the cost of energy to operate it for the month of August.

A washing machine rated 300 W operates one hour/day. If the cost of a unit is Rs. 3.00 , find the cost of the energy of operate the washing machine for the month of March.

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)