Four coins.
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The complement is "Not four heads", that is, at least one tails.
1heads heads heads 2heads heads tails 3heads tails heads 4heads tails tails 5tails tails tails 6tails tails heads 7tails heads tails 8tails heads heads
Because you are thinking permutations rather than combinations. There are four permutations of two coins, but there are only three combinations, because it does not matter which coin is heads and which coin is tails. As a result, the combination of heads and tails has a 0.5 probability, while two heads or two tails each have a 0.25 probability.
There are 8 possible outcomes when a coin is tossed 3 times. Here they are:1. Heads, Heads, Tails.2. Heads, Tails, Heads.3. Tails, Heads, Heads.4. Heads, Heads, Heads.5. Tails, Tails, Heads.6. Tails, Heads, Tails.7. Heads, Tails, Tails.8. Tails, Tails, Tails.There is only one outcome that is heads, heads, heads, so the probability of three heads coming up in three coin tosses is 1 in 8 or 0.125 for that probability.
Four lizards, is one possible answer.