In Chinese, 几(jǐ) and 多少(duōshao) are frequently used to ask questions about numbers or quantities. There seem very similar, but quite different in usage.
1. 几 is usually used to ask about or refer to uncertain numbers not higher than ten.
你几岁？（Nǐ jǐ suì?）How old are you?
现在几点？ （Xiànzài jǐ diǎn?）What time is it now?
2. It`s followed by measure words.
几 + measure word + (noun)
你来北京玩几天？ （Nǐ lái běijīng wán jǐ tiān?）How many days are you going to stay in Beijing?
你看了几本书？ （Nǐ kànle jǐ běn shū?）How many books have you read?
3. It can be used to replace the single digits when the uncertain number is higher than ten.
我家有十几口人。 （Wǒjiā yǒu shí jǐ kǒu rén.）There are more than 10 people in my family.
我有五十几块钱。 （Wǒ yǒu wǔshí jǐ kuài qián.）I have more than 50 yuan.
1. It can be used to ask about or refer to any number.
2. Measure words can be omitted between “多少” and nouns.
你看了多少（部）电影？ （Nǐ kànle duōshǎo (bù) diànyǐng?）How many movies have you watched?
她有多少（个）学生？ （Tā yǒu duōshǎo (gè) xuéshēng?）How many students does she have?