A person walks along a straight path at a constant speed of 2 m/s. How long does it take to cover 780 m? Give the answer in minutes and seconds.

Step-by-step solution

1. 1

   Rearrange the uniform-motion formula. From $v=\dfrac{s}{t}$ we solve for the unknown time: $t=\frac{s}{v}$

2. 2

   Check that the units already agree. The distance is in metres and the speed in metres per second, so the quotient is in seconds directly — no conversion is needed before dividing.

3. 3

   Substitute the given values. $t=\frac{780\text{ m}}{2\text{ m/s}}=390\text{ s}$

4. 4

   Convert seconds into minutes and seconds. Divide by $60$: $390=6\times 60+30$, so $390\text{ s}=6\text{ min }30\text{ s}$

5. 5

   Select the option. The matching choice is C. Note that $6\text{ min }15\text{ s}=375\text{ s}$ and $7\text{ min }30\text{ s}=450\text{ s}$, neither of which equals $390\text{ s}$.