The "Yankee" is a 4 selection wager consisting of 11 bets: 6 doubles, 4 trebles and a four-fold accumulator. The yankee is rumored to be named after an American soldier that placed a small bet in the UK and due to the multiple roll-over mechanics at work won back hundreds of thousands.
This is a full cover bet where each selection appears in 3 doubles, 3 trebles and the four-fold accumulator. To understand how winnings change with outcome, stake size and odds most people prefer to use a yankee calculator, both before placing a bet and after the outcomes are known. Two or more winning choices guarantees a return from this wager.