We are given that the total number of students is 400. Let:
The total number of students is:
\[ x + 3x = 400 \]
Solving for \( x \):
\[ 4x = 400 \Rightarrow x = 100 \]
Thus:
\[ 210 + 60 = 270 \]
\[ \frac{270}{400} \times 100 = 67.5\% \]
Thus, the percentage of students who walk to school is 67.5%.
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?