Question

The child's foot and tooth is aching rewrite the following sentence from singular to plural

Answer 1

Here the correct form will be, “The child’s feet and teeth are aching.”

The tooth and foot are the singular forms of words, when we say foot or tooth, we are talking about the single one but to convert them into plural form, you need to use feet or teeth.

Here the child can be written as children as well.  

Answer 2

Noun is a name of a person, place, thing.

A singular noun names one person, place, thing, or idea, while a plural noun names more than one person, place, thing, or idea.

So writing the sentence in plural noun will be “The child's feet and tooth are aching aching”