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.

• If you don't like it, don't use it. It's recorded in the OED from 1877 in the specialised world of building and surveying, and from 1962 in general use. Commented Nov 20, 2013 at 14:00
• I am nonplussed!
– Kris
Commented Nov 29, 2013 at 14:30

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?

• Thoughts on removing the personal anecdote from this otherwise excellent answer? Commented Nov 19, 2017 at 20:32

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.

• I agree wholeheartedly and I think the described use of times or minus is an abomination. Very small children, understandably, get confused and use the wrong words, but in addition to being technically wrong, this misuse of terms demonstrates a lack of understanding of math. Mathematics is a world of very precise definitions where it is important to keep the language clean. Commented Nov 20, 2013 at 16:01
• I can't understand teachers ever using it. If they do, how can children ever learn the correct way of saying things? Commented Feb 11, 2014 at 14:13

It's not formal English, but it's certainly in widespread use.

It stems from "12 times 12 equals 144", meaning "Taking 12, 12 times, you'll have 144".

"Times" here is a noun, but its use and position in the sentence makes it sound like a verb giving way to new constructs such as:

I times 5 by 5 to get 25...
You can times 10 by 9 to get 90...
20 timesed [sic] by 15 equals 300

The formal equivalent is "multiply".

“To times” is not a verb, therefore “times it by one hundred” is incorrect.

But yes language is dynamic and teachers are using it so, sadly, it looks set to become common parlance. In fact I’d say it already has.

Most annoying: You can't "subtract by a number." You can subtract a number FROM another number but not "by." Save by for multiply by or divide by.