Question 482971
Assuming you mean:
A swimming pool is 50 meters long. A boy can swim across the length and then return to his starting position in 5 MINUTES. 
What is his swimming speed in km/hr?
:
Find the meter/min, multiply by 60 to get meter/hr, divide by 1000 to get km/hr
{{{100/5}}} * 60 * {{{1/1000}}} = 1.2 km/hr