According to Yahoo Sports:

British horse racing officials plan to experiment with a simpler way to list odds in a bid to encourage younger people to take an interest in the sport.

Concerned that figures such as 100-30 and 8-11 confuse newcomers to racing, Racing Enterprises Ltd, the commercial arm of British horse racing, wants to introduce decimalized odds and conduct an experiment over a weekend’s racing in a few months time.
Under the experiment, 100-30 will be 4.33 and 8-11 becomes 1.72, with the decimalized odds including the stake money—in other words, showing that a one-pound bet would return 4.33 pounds in the first example.

“Decimal odds are inevitable, whether they come in a year, five years or 10 years, or earlier,” Simon Clare, trading director of bookmakers Coral, said Tuesday. “But this is a trial and its successful implementation will be all about communication and presentation so that regular customers are not alienated while younger customers are encouraged to look at betting on horse racing.”

But some bookmakers argue that the decimalized odds are just as tricky to understand and that, although they are a thing of the future, more consultation is needed before they replace the long standing existing odds which have been in use for over a century.

“The new generation are more used to decimalization than some of us but some of these odds are more confusing,” said William Hill spokesman David Hood. “Such as 6-4, which is 1.5-1, and that becomes 2.5 if you include the stake money. And 7-2, for example, becomes 4.5.

(Editor’s Note: Huh??)