Question

Suppose in a house there are five bulbs of $100W$ each, four of $60W$ each and six of $40W$ each. All of them are used for two hours a day. After $30$ days, how much will they have to pay at $Rs.3.0/-$per unit?

• A. $Rs.168.0/-$
• B. $Rs.171.2/-$
• C. $Rs.174.0/-$
• D. $Rs.174.6/-$

Answer 1

The correct option is D $Rs.174.6/-$

Total power used
$=(5\times 100W)+(4\times 60W)+(6\times 40W)=980W=0.98KW$Total power used everyday
$=2h\times 0.98KW=1.96KWH$In 30 days, the power used
$=30\times 1.96KWH=58.8KWH$The cost of the power is
$=Rs.3\times 58.8=Rs.176.4/-$