For those who would like a hint.
In English, “And” generally indicates addition, “Per” division.
Now consider which of the following makes sense:
Ferrets and seconds
Ferrets per second
But apples and pears makes sense, whereas apples per pear doesn’t (much)
if you’re checking how many fruits you have, “apples and pears” makes sense.
If you’re trading a bag of apples for a bag of pears, you might want to know the relative value of apples and pears, so you would indeed calculate “apples per pear”.
Neither
For those who would like a hint.
In English, “And” generally indicates addition, “Per” division.
Now consider which of the following makes sense:
Ferrets and seconds
Ferrets per second
But apples and pears makes sense, whereas apples per pear doesn’t (much)
if you’re checking how many fruits you have, “apples and pears” makes sense.
If you’re trading a bag of apples for a bag of pears, you might want to know the relative value of apples and pears, so you would indeed calculate “apples per pear”.
Neither