Question

Greene ran the 100-meter dash in 9.79 seconds. What was his speed in kilometers per hour (round to the nearest kilometer)?

Answer 1

$1m \ \ is\ \ \frac{1}{1000}km\\ 100m\ \ is\ \ \frac{1}{10}km\\ 1s\ \ is\ \ \frac{1}{3600}h\\ 9,79s\ \ is\ \ \frac{9,79}{3600}h\\\\ \frac{100meters}{9,79\ seconds}=\frac{100}{97}*\frac{\frac{1}{10}}{\frac{9,79}{3600}}=\frac{100}{97}*\frac{1}{10}*\frac{3600}{9,79}=\frac{360000}{970*9,79}=\\ \frac{360000}{9496,3}\approx\boxed{37,9\frac{km}{h}}$