An accumulator combines two or more selections into a single bet whose odds are the product of the individual prices. Three picks at 1.50 × 1.72 × 1.85 pay 4.77 — attractive, which is why accas are heavily marketed. The catch: one losing leg sinks the whole ticket, and the bookmaker's margin compounds with every leg you add.
If each leg carries a 5% margin, a treble bakes in roughly a 14% house edge before kick-off. That makes long accumulators structurally poor value — entertainment first, investment never. If you do combine, keep legs few, hunt the best price on each individually, and stake small: the correct expectation for an acca is an occasional fun win, not steady profit.
Three legs, each fairly 60% likely: combined true probability = 0.6³ = 21.6% (fair odds 4.63). Priced legs of 1.58 each give a payout of 3.94 — implying 25.4% and handing the book a compounded ~18% margin on the ticket.