grammatical number - ...the probability of flipping exactly one head[s] and three tails

I've encountered the following math question:

Four fair coins are tossed at the same time. What is the possibility that the four coins will come up with only one head and three tails.

Besides wanting to change "possibility" to "probability," and "only" to "exactly," I wonder about the word head. In coin-flipping, we typically use this word in the plural (and I understand there's a post about the history of "heads or tails"). But always?

My gut tells me to keep it plural. However, a bit of digging turned up examples for both singular and plural used in this type of context.

For example, Statistics: A Guide to the Use of Statistical Methods in the Physical Sciences contains the following:

For one head and three tails, the probability is the same as one tail and three heads.

It still sounds awkward to me, as do other usages in the same book, such as:

The probability of the first coin giving a head is ½.

I'd definitely avoid that phrasing, particularly for the college crowd.

In any case, head or heads in the listed contexts?