Question

A washing machine rated $300W$ is operated one and half an hour/day. If the cost of units is Rs.$3.50$, find the cost of energy to operate a washing machine for the month of September.

• A. Rs.$27.90$
• B. Rs.$35.25$
• C. Rs.$47.25$
• D. Rs.$55.90$

Answer 1

Answer: (C)

Rs.$47.25$

Now, the units consumed (kWh) $=$ power (kW) x time (hours)

There are 30 days in the month of September, thus 1.5x30 $=$ 45 hours

Thus the number of units is given by $300$ x ${10}^{-3}$ x 45

Total number of units $=$ 13.5 units

Thus the energy cost for 13.5 units is 13.5 x 3.5 $=$Rs 47.25$