If william runs 5 meters in 20 steps how many kilometers will he run after taking 1000 steps

1000/20=50
50•5= 250
It will take 250 meters to run 1000 steps.

5m/20 steps =?/1000 steps 
You have to use ratios at first to determine the unknown  

then divide 1000 by 20 to get the multiplying factor which is 50, now you multiply 50 by 5m to get the unknown in meters, there you just convert meters to km. 50x5 = 250 meters, 250 meters = 0.25km . At this rate, William will run .25 km after taking 1000 steps.