The Duckworth-Lewis method is used to help decide rain-interrupted one-day cricket matches.
It is named after Frank Duckworth and Tony Lewis who devised the mathematical formula.
It means a result can always be reached in a reduced overs match.
WHEN IS IT USED?
Teams start a match with the same resources - the number of overs they receive and number of wickets in hand.
If a match is shortened once it is started, so the resources are reduced.
For example, if the team which bats first had their innings interrupted, team two would often be set a larger run target to compensate.
But should the team second at the stumps be interrupted, their run target would often be reduced.
Duckworth and Lewis came up with the equation which determines how much a run target should be altered.
HOW DOES IT WORK?
For example: a team have lost five wickets after receiving 25 of their 50 overs when rain stops play.
At this point, using the table produced by the Duckworth-Lewis method, the team's remaining resources are valued at 42.2%.
If 15 overs are then lost because of the weather, the innings will be completed after only 10 more overs.
The D/L method says that, with 10 overs left and five wickets lost, the team has 26.1% of their resources left.
To compensate for the lost overs, we must calculate the resource % lost.
This works out to 42.2 - 26.1 = 16.1.
If the team had been chasing a total of 250 runs, their new target is calculated in the following way.
Resources available at the start = 100%
Resources lost = 16.1
Resources available after rain interruption = 83.9%
Then reduce team one's score in the following way. Multiply team one's runs scored by the recalculated resources divided by the resources available at the start.
That is: 250 x 83.9/100 = 209.75.
The target is then rounded to the nearest whole number, so the team batting second would be set a target of 210 to win.