80 miles an hour divided by 60 gives 80/60=4/3 miles per minute. That's one and a third miles a minute. Divide by 60 again and we get 4/180 miles a second = 1/45 miles per second. So there's a fraction. There are 1760 yards in a mile so multiply 1/45 by 1760 to find the speed in yards a second=352/9=39 and one ninth yards per sec. There are three feet in a yard, so multiply by 3 and we get 117 feet 4 inches (12 inches in a foot, and one ninth of a yard is 4 inches) per sec. Multiply 117 by 12 to convert feet to inches and add on 4 inches=1408 inches per second. 1 inch = 2.54 cm, so 1408 inches = 3576.32 cm = 35.7632 metres per second. Multiply by 3600 to get this to metres per hour (3600 seconds in an hour) =128747.52 metres per hour=128.74753 kilometres per hour.