how many there areUsed after a noun ending in a vowel-consonant subject marker combination, as in 사람이 얼마나 많은지. The pattern 얼마나 많은지 can also mean “how much there is” or “how many ... there are,” depending on the noun. It can introduce an embedded question or emphasize a surprisingly large amount.
KO: 이 동네에 식당이 얼마나 많은지 알아?
EN: Do you know how many restaurants there are in this neighborhood?