We say that q is the quotient and r the remainder obtained when b is divided into a.


The underlined part, "b is divided into a", is it correct expression?

"when a is divided by b" seems to be absolutely correct, but "when b is divided into a" is pretty unfamiliar to me....
Imagine you have 10 and you divide it into 5 different portions, you get 2 each. Got it?
Got it!!!