The number of multiple births in the united states for a recent year indicated that there were 128665 sets of twins, 7110 sets of triplets, 468 sets of quadruplets, and 85 sets of quintuplets. choose on set of siblings at random. find the probability that it represented quads or quints

OK, so since the twins are 2 babies and triplets are 3 babies and quadruplets are 4 babies then the chance you get a quadruplet baby is higher than their relative birth occurence, because they're double the babies!! right? so in fact, to get the chance of a triplet baby, you divide the number of triplets*3 (three babies for every triplet) with (twins x 2 +triplets x 3 +quadruplets x 4 +quintuplets x5)'

there is only 85 quintuplets, but they introduce 425 babies so you have to multiply the 85 quintuplets with 5

The first option would be correct if it were one half and not one