Pan holding the 206 gram weight tipping down

Six weights of $201, 202, 203, 204, 205$ and $206$ grams are split at random into two groups of three, one group on each pan of a balance. What is the probability that the pan carrying the $206$-gram weight is the heavier one?

$\tfrac45$. Subtract $200$ from each weight; the masses become $1$ to $6$ with total $21$, and the pan with $6$ is heavier when its two partners sum to at least $5$. Of the $\binom52=10$ equally likely partner pairs, only $\{1,2\}$ and $\{1,3\}$ fail.