This is a ratio problem where you set 2/8 km / 3 minutes = 1 / x. Simplifying:
2/24=1/x
Cross multiply: 1*24/2=12. So it takes 12 minutes.
Actually this makes sense because 2/8 is 1/4 of a km so it should take four times longer or 3*4 to run a full km.
Hope that helps!
