Question

. A house has 3 tube lights, two fans and a Television.
Each tube light draws 40W. The fan draws 80W and
the Television draws 60W. On the average, all the
tube lights are kept on for five hours, two fans for 12
hours and the television for five hours every day. Find
the cost of electric energy used in 30 days at the rate
of Rs. 3.00 per kwh. (AST)​

Answer 1

Given :

• A house has 3 tube lights, 2 fans, 1 television
• Each tube light draws 40 W ; each fan draws 80 W and; each Television draws 60 W
• All the tube lights are kept on for 5 hours ; two fans for 12 hours and the television for 5 hours each day

Two find :

• Cost of electric energy used in 30 days at the rate of Rs 3.00 per kWh .

Knowledge required :

• electrical Energy consumed = power × time

Solution :

▶ Calculating total energy consumed by 3 tube lights , two fans and a television in 30 days

• energy consumed by 3 tube lights in 30 days, each of which is of power 40 W and is used 5 hours daily  = ( 3  × 40  × 5  ) × 30 = 18000 Wh = 18 kWh

• energy consumed by 2 fans in 30 days, each of which is of power 80 W and is used for 12 hours daily = ( 2 × 80 × 12 ) × 30 = 57600 Wh = 57.6 kWh

• energy consumed by a television in 30 days, draws a power of 60 W and is used for 5 hours daily = ( 1 × 60 × 5 ) × 30 = 9000 Wh = 9 kWh

therefore,

→ Total energy consumption is 30 days = 18 + 57.6 + 9

→ Total energy consumption is 30 days = 84.6 kWh

▶ Calculating the cost of electric energy used in 30 days at the rate of Rs 3.00 per kWh

→ Cost of Electrical energy = 84.6 × 3.00   Rs

→ Cost of electrical energy = 253.80  Rs

therefore,

• Total cost of energy consumed is Rs 253.80.

Answer 2

Explanation:

Given that, three tube lights, two

fan's and a TV are in a house.

Power consumed by one tube light = 40W

Power consumed by three tube light = 3*40W = 120W

Also given in question that, each tubelight is kept on for 5 hours.

So, Energy consumed by tube light = 5*120W = 600W ..........(1)

Power consumed by one fan = 80W

Power consumed by two fan = 2*80W =

160W

Each fan is kept on for 12 hours. So,

Energy consumed by fan = 12*160W = 1920W ...........(2)

Power consumed by TV = 60W

TV kept on for 5 hours

Energy consumed = 5*60W = 300W .......(3)

Consumption of energy in one day = 600 + 1920 + 300 = 2820W = 2.820kW

The cost of electric energy used in 30 days at the rate of Rs. 3.00 per kwh.

= 2.820 × 3.00 × 30

= Rs. 253.8