We are given the equation:
\[ B = \frac{5}{2} A \]
Rearrange the equation to solve for \( A \):
\[ A = \frac{2}{5} B \]
The percentage of \( A \) in \( B \) is given by:
\[ \frac{A}{B} \times 100 \]
Substituting \( A = \frac{2}{5} B \):
\[ \frac{\frac{2}{5} B}{B} \times 100 \]
Canceling \( B \):
\[ \frac{2}{5} \times 100 = 40\% \]
Thus, the correct answer is 40% (Option A).
An electricity utility company charges ₹7 per kWh. If a 40-watt desk light is left on for 10 hours each night for 180 days, what would be the cost of energy consumption? If the desk light is on for 2 more hours each night for the 180 days, what would be the percentage-increase in the cost of energy consumption?