Accumulator / parlay

Same bet, two names. In Britain and Ireland it is an accumulator. In North America it is a parlay. One stake, every selection must win. Add legs up to 100.

Work it by hand

Convert every price to decimal, then multiply. Decimal is simply “what £1 comes back”. Fractional 5/2 is 3.50. American +150 is 2.50. A three-leg parlay at 3.50, 2.50 and 2.10 is 3.50 × 2.50 × 2.10 = 18.375. A £10 stake returns £183.75. Profit is returns minus the stake: £173.75.

One loser and the whole ticket is dead. That is the difference between a parlay and a Trixie or Lucky 15, which still have doubles standing if one selection is beaten.