Breakdown of Сколько машин едет по мосту?
машина
car
ехать
to go (by vehicle)
сколько
how much / how long / as much / as many as
по
along, around
Questions & Answers about Сколько машин едет по мосту?
Why do we use по here instead of на for "on the bridge"?
In Russian, по with the Dative case (мосту) is used for movement along a surface. While English says "driving on the bridge", Russian expresses this as driving along the length of it. If you used на with the Prepositional case (на мосту), it would focus on their static location rather than their movement along the path.
Since we are asking about multiple cars, why is the verb едет in the singular form instead of the plural едут?
When a sentence has a quantity word like сколько (how many), the verb usually takes the third-person singular form. Grammatically, the sentence is treating the "amount" of cars as a single unit performing the action.
Why is the word for cars spelled машин here?
The question word сколько requires the noun that follows it to be in the Genitive case. Since we are asking about multiple cars, we use the Genitive plural form of машина, which drops the ending vowel to become машин.
Why use едет instead of another motion verb like ездит?
We use едет because the question is about cars making a single, one-way trip along the bridge right now. If we were asking about cars that drive back and forth across the bridge every day as a general habit, we would use the multidirectional verb ездит instead.