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I know that "much" is used for uncountable nouns like money,rice...etc.For "How much",we can say how much money do you have ?.

Is it that How much(asking for a price/cost of something)can be used with plural nouns,like how much are these tomatoes ?If it's the case,I found also these questions and I didn't understand when do we have to use how much is and are ?

-How much is the hamburger ?

-How much is the hamburger and French Fries ?Why didn't they say how much are the hamburger and French Fries ?
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When mixing singular and plural nouns the verb usually agrees with the nearest noun (in your example is agrees with the hamburger).

How much are the hamburger and French fries? (also correct but less common)
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everlastinghopeIs it that How much(asking for a price/cost of something)can be used with plural nouns,like how much are these tomatoes ?
Correct.
everlastinghope
-How much is the hamburger and French Fries ?Why didn't they say how much are the hamburger and French Fries ?

"hamburger and French fries" is considered to be one item (one meal).
Mr Wordy
"hamburger and French fries" is considered to be one item (one meal).

What about if they are two different meals ?I mean separately.You ask for the price of hamburger,then French fries.
everlastinghope
What about if they are two different meals ?I mean separately.You ask for the price of hamburger,then French fries.

I think that Ivanhr's answer is better than mine actually. The most natural pattern is probably just to make the verb agree with the nearest noun.
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