Deconstructing the QuestionThe problem asks for the time difference between Tom and John covering the same distance (from the passing point to the Gas Station).
Since the Distance is constant, we can use the
Ratio Method instead of calculating specific distances.
- Tom's Speed (\(S_T\)): 15 km/h
- John's Speed (\(S_J\)): 10 km/h
- Tom's Time (\(t_T\)): 15 minutes
Step 1: Determine the RatiosCalculate the ratio of their speeds:
\(\frac{S_T}{S_J} = \frac{15}{10} = \frac{3}{2}\)
Since Speed and Time are
inversely proportional for a constant distance:
\(\frac{t_J}{t_T} = \frac{3}{2}\) (John takes 3 units of time for every 2 units Tom takes).
Step 2: Calculate John's Total TimeWe know Tom takes 15 minutes. Let's solve for John's time (\(t_J\)):
\(t_J = t_T \times \frac{3}{2}\)
\(t_J = 15 \times 1.5 = 22.5 \text{ minutes}\)
Step 3: Interpret the Question ContextThe calculated total time for John is
22.5 minutes. Looking at the options (5, 6, 7.5...), none match the total time.
The question phrasing implies: "How many
more minutes does it take John to arrive
after Tom has arrived?"
\(\text{Time Difference} = t_J - t_T\)
\(\text{Time Difference} = 22.5 - 15 = 7.5 \text{ minutes}\)
This matches option C perfectly.
Answer: C