The usage of "по" in distributive expression

Question

In a text, used for educational purposes, were the following sentence:

Каждый ученик получил по красному карандашу.

Based on the context, I could translate this into "Each student received a red pencil". Is the translation correct? The bothering thing here is the part по красному карандашу - which could indicate a lot of different things, as по has vast variety of applications.

As I see it, the sentence could just be written as

Каждый ученик получил красный карандаш.

My question is: Does this kind form (по + dative) in this kind of context also convey some other information? Why is it used and what is the grammar behind this kind of usage?

Answer 1

По here conveys a similar meaning as "each" would in English.

Every student received a red pencil. Vs Every student received a red pencil each.

Although it's pretty obvious here that each student got their own pencil, especially with the "Каждый" construction, instead of "Все ученики..", where it could possibly be interpreted that all students collectively received a single red pencil, it's more of a stylistic choice that conveys unambiguously that each student got one red pencil each.

This construction can also be used in the case of multiples, like по два карандаша, по пятнадцать карандашей, etc. (Two each, fifteen each)

Answer 2

Just to add to the answer given (which is 100% correct) - "по" is insanely productive preposition in Russian and it is used in a wide variety of scenarios. Here one can find dozens of examples of different usages and this list is still incomplete because there are some other colloquial usages ("заседать по газу", "по любому") and even obscene phrases like "пошёл по пизде".

Being back to this particular usage - there are some scenarios when you just can not omit "по" because it won't be even disambiguation but rather a sentence with slightly different meaning. Compare:

Тесты гоняются 20 минут.

and

Тесты гоняются по 20 минут.

First is about the fact that tests are running for 20 minutes. May be it's always the case, may be it's just only about this run. Second sentence is about the fact that it takes 20 minutes to run tests each time.

Or consider following example:

Ученикам на выполнение контрольной дали 20 минут.

and

Участникам школьных дебатов дали по 20 минут.

First sentence here states that all pupils were given 20 minutes, second is about the fact that every student has 20 minutes to prepare.