Question

The monthly electricity bill in a hostel for lighting $22$ bulbs each of $100$ watt for $6$ hours daily is $Rs.3520$. Then the amount of the bill when $30$ bulbs each of $100$ watt are lighted for $8$ hours daily is:

• A. $Rs.3200$
• B. $Rs.4800$
• C. $Rs.5800$
• D. $Rs.6400$

Answer 1

The correct option is D $Rs.6400$

The cost of lighting $22$ bulbs for $6$ hours daily $=Rs.3520$

$\therefore$ The cost of lighting $1$ bulb for $1$ hour daily $=Rs.\frac{3520}{22\times 6}$

$\therefore$ The cost of lighting $30$ bulbs for $8$ hours daily $=Rs.\frac{3520\times 30\times 8}{22\times 6}=Rs.6400$.