I was talking with a child who, I was told, has learned some basic multiplication that he can do in his head, so I asked him Сколько будет восемь на семь
?
I'm not a native speaker, but I've given lectures in Russian on higher math and I say just на
in place of умножить на
and разделить на
; the context makes it obvious which one is meant. With the child also it was obvious (to me) that I meant multiplication, since division, square roots, etc. are not yet part of the child's lexicon.
Anyway, the parent corrected me by repeating the task but said восемь умножить на семь
. That made me realize that perhaps when children learn multiplication this operation is always given in the form умножить на
instead of на
.
When does the transition usually take place to abbreviate multiplication (and division) to на
when the choice is clear from context?