Answer:
The coefficient 1.5 means her winning distance is 1.5 times the mean (add them up and divide the total number by the number of numbers) of her three best practices.
Some other helpful stuff:
Let's say Rosa's three practice distances were 1.6 meters, 1.7 meters, and 2.1 meters. To get the mean of these, add them up(5.4) and divide by the number of numbers, three(1.8). Let's say her winning distance was 2.7. If you divide the winning time by the mean of her three best practices, you get 1.5. This means that 2.7 = 1.5(1.8), or, 2.7 = 1.5M.