Is 'times it by' or 'minus it by' correct?

I'm always hearing math instructors, and students, use ‘times it by’ to describe multiplicative operations:

“…To find the ratio, you times it by one hundred…”

To hear other students phrasing mathematical operations like this is one thing, but hearing my math instructors using this really bugs me. Could it possibly be correct? It sounds quite off to me.

I remember this usage from when I was in primary school, and I never adopted it. There are speakers, like me, for whom plus, minus and times are, in mathematics (the topic of my undergraduate degree), only the names of the operations +, -, and x. The corresponding verbs are add, subtract, and multiply.

For example, I’d say:

• To find the percentage, you multiply [not times] the ratio by 100.
• To find the mean, you add [not plus] the given n numbers together, then divide by n.
• To find the range, you subtract [not minus] the lowest number from the highest.

That said, if enough (influential) people start using plus, minus and times as verbs, then, as with every other language change, that will eventually come to be regarded as standard and, hence, correct. After all, if you can hammer with a hammer, and plough with a plough, why shouldn’t you be able to plus with a plus?

Sounds off to me too Austin, but the awful habit exists in Britain too. I can understand teachers of primary-school children using it. But I think we have a right to expect that teachers of children over the age of 11 speak to them in adult English.

Should be 'multiply it by' or 'subtract x amount from' etc.