Hello, I am Yoshi from NILS Japnaese langauge school.
[Saying numbers #2]
4) Interrogatives
A) いくつ is used to ask how many about the things which are counted as ひとつ, ふたつ, ・・・・・・.
(Example)
みかんを　いくつ　買いましたか。　　—8つ　買いました。
How many mandarin oranges did you buy?　　—I bought eight.

B) なん is used with a counter suffix to ask how many.
(Example)
この会社に　外国人が　何人（なんにん）　いますか。　　—5人　います。
How meany foreigners are there in this office.　　—There are five.

C) どのくらい is used o ask the length of time somehing takes. You can use various units of time int he answer.
(Example)
どのくらい　日本語を　勉強しましたか。　　—3年　勉強しました。
How long did you study Japanese?　　—I studied it for three years.

5) ぐらい： ぐらい is added after quantifiers to mean “about.”
(Example)
15分ぐらい　かかります。
It takes about fifteen minutes.

August 9th News, from NILS Japanese language school.