Question

A person crosses a \(600\ \text{m}\) long street in \(5\) minutes. What is his speed in km per hour?

• A. \(3.6\)
• B. \(7.2\)
• C. \(8.4\)
• D. \(10\)

Hint:

Always match units before calculating speed. Convert minutes to hours for km/h, or seconds to hours for m/s conversions.

Answer 1

The Correct Option is B

Step 1 (Identify given values).
Distance covered \(= 600\ \text{m}\).
Time taken \(= 5\) minutes.
Step 2 (Convert time to hours for km/h calculation).
\(5\) minutes \(= \dfrac{5}{60} \ \text{hours} = \dfrac{1}{12} \ \text{hours}\).
Step 3 (Convert distance to kilometers).
\(600\ \text{m} = 0.6\ \text{km}\).
Step 4 (Use speed formula).
Speed \(= \dfrac{\text{distance}}{\text{time}} = \dfrac{0.6}{\frac{1}{12}} = 0.6 \times 12 = 7.2\ \text{km/h}\).
Step 5 (Verification).
In \(1\) hour at \(7.2\ \text{km/h}\) \(7.2\) km = \(7200\) m.
In \(\frac{1}{12}\) hour, distance = \(\frac{7200}{12} = 600\ \text{m}\) ✔.
\[ \boxed{7.2\ \text{km/h (Option (b)}} \]