People must not forget that "one" is the subject for this sentence. Since the subject is singular, it needs a singular form of a verb, thus "approves" is correct here.
One in ten means more than one... So that we should say "approve". Thank you!
Sorry, but Shin is correct.
"One" is the subject of the sentence. It should be "One in ten approves...."
"One in ten approve of the idea." is correct.
"One in ten approves of the idea" is wrong.
"Three in five approves of the idea" is wrong.
"Three in five approve of the idea" is correct.
'X in Y' is the subject and is always treated as plural. Thus: approve.