Question

In a house 5 bulbs of 25w each are used for 6hrs a day. Calculate the units of electricity consumped in a month of 30 days. Aalso find the total expenditure if 1 unit electricity costs ₹1.50

Answer 1

$energy = (125 \times 6 \times 30) \div 1000 \\ = 22.5units \\ cost = 22.5 \times 1.50 \\ = 33.75rupees$

Answer 2

Power

Total number of bulbs in the house $=5$

Power of each bulb $=25 \ W$

Power of 5 bulbs $= 25\times 5 = 125 \ W$ $=0.125 \ kW$

Number of hours  a bulb is on in a day $= 6 \ hours$

Number of hours power used in 30 days $= 30\times 6= 180 \ hours$

Electricity consumed in a day $=0.125\times 6=0.75 \ kW\ hour$

Electricity consumed in 30 days $= 0.75\ times 30=22.5 \ kilowatt \ hour$

As we know that ,

$1 \ unit = 1 \ kWh$

Cost of 1 unit electricity $= Rs. \ 1.50$

Total expenditure on electricity $= 1.5\times 22.5= 33.75$

Hence, cost will be Rs. 33.75.