A paragraph could very well be one sentence, but it could just as easily be a long 20 sentence paragraph. It's usually thought of as being a complete separate thought and containing as many sentences are needed before you reach a natural breaking point to move on to the next paragraph. Hope that helped.
Centi-means one-hundredth, so 1metre = 100 centimeters, therefore 1 decameter = 10 x (100 centimeters) = 1000 centimeters. Hecto-means one hundred, therefore 1 hectometer = 100 meters = 10 decameters. Kilo-means one thousand, of course, so 1 kilometer = 1000 meters, and since 1 hectometer = 100 meters, 1 kilometer = 10 hectometers.
How many kilometers is 250 meters? The distance of 250 meters is equal to 0.25 kilometers. One kilometer (K) is equal to 1000 meters (M), so the formula M / 1000 = K is used to convert meters to kilometers. Alternatively, one could use M * 0.001 = K to covert the numbers as well.