Question

Ms. Anita uses a BS-IV two-wheeler petrol scooter (mileage $=50$ km/L) to travel $30$ km every day. She exchanges this with an electric scooter that consumes electricity at $0.1$ kWh per $10$ km (i.e., $0.01$ kWh/km). Petrol and electricity prices are Rs. $90$/L and Rs. $3.5$/kWh, respectively. Maintenance costs of both are negligible. The \emph{operational cost saved in a year} is __________________ (in Rs., in integer).

Hint:

Normalize everything to \textbf{per km} first. Multiply by distance to get daily cost, then scale by the number of days. Rounding to integer is typically by the nearest rupee unless otherwise stated.

Answer 1

Correct Answer: 19300

Step 1: Convert all given performance numbers to ``per km'' costs.
Petrol scooter: Mileage $=50$ km/L $\Rightarrow$ fuel per km $=\dfrac{1}{50}$ L/km.
Cost per km $=\dfrac{1}{50}\times 90=\boxed{1.80\ \text{Rs./km}}$.
Electric scooter: Use $0.1$ kWh/10 km $\Rightarrow 0.01$ kWh/km.
Cost per km $=0.01\times 3.5=\boxed{0.035\ \text{Rs./km}}$.
Step 2: Daily operating cost for 30 km.
Petrol: $30\times 1.80= \boxed{54.00\ \text{Rs./day}}$.
Electric: $30\times 0.035= \boxed{1.05\ \text{Rs./day}}$.
Step 3: Daily savings and annual savings (assuming 365 days).
Saving/day $=54.00-1.05=\boxed{52.95\ \text{Rs./day}}$.
Saving/year $=52.95\times 365=\boxed{19{,}326.75\ \text{Rs.}}$
Report as integer $\Rightarrow \boxed{19{,}327\ \text{Rs.}}$. Final Answer:\fbox{19{,}327 Rs.}