7 ways to use approximate numbers in Chinese

Using two neighboring numbers

相邻的两个数连用

Examples:

five or six eggs (五六个鸡蛋-wǔ liù gè jī dàn)

about seventeen or eighteen years old (十七八岁- shí qī bā suì) 

about two or three hundred bottles of water (二三百瓶水-liǎng sān bǎi píng shuǐ)

about one or two thousand people (一两千人- yī liǎng qiān rén)

Structure: numeral+多(duō) or 来(lái) or 左右(zuǒ yòu) or 上下(shàng xià) or 开外 (kāi wài)

结构：数词+"多／来／左右／上下／开外"

number +多(duō)

over ten books (十多本书-shí duō běn shū) 

over five hundred years (五百多年- wǔ bǎi duō nián) 

over four months (四个多月- sì gè duō yuè)

number+来(lái)

numeral ends with zero+来+measure word

数词（以零结尾的）十"来"十量词

about sixty years old (六十来岁- liù shí lái suì) 

about thirty basketballs (三十来个篮球- sān shí lái gè lán qiú)

about forty jin rice (四十来斤大米- sì shí lái jīn dà mǐ) (a jin is 500g)

numeral+ meter measure word+来+adjective

数词+度量衡量词+"来"+形容词

about three meters long (三米来长- sān mǐ lái cháng)

about one meter wide (一米来宽- yī mǐ lái kuān)

左右(zuǒ yòu)

"左右(zuǒ yòu)" can be used after time words or measure words with approximate numbers. It applies to many situations. For example:

表示大概的数，可以放在时间词、数量词等后面，使用范围比较广。例如：

about ten days (十天左右- shí tiān zuǒ yòu)

about eight hundred people (八百人左右- bā bǎi rén zuǒ yòu)

about 1.7m (一米七左右- yī mǐ qī zuǒ yòu)

上下 (shàng xià)

"上下(shàng xià)" is used with approximate numbers, indicating age, height or weight. For example:

表示大概的数，多用来表示年龄、高度和重量。例如：

about thirty years old (三十岁上下- sān shí suì shàng xià) 

about two meters high (两米上下- liǎng mǐ shàng xià) 

about 60kg (六十千克上下- liù shí qiān kè shàng xià)

开外 (kāi wài)

Used after numerals or quantifiers (referring to age or distance), "开外(kāi wài)" means something is beyond a certain quantity. For example:

用在数词或数量词（多表示年龄或距离）后面，表示超出这个数量。例如：

她今年四十开外。（四十多岁）

tā jīn nián sì shí kāi wài.

She is over forty years old.

两地的距离六十里开外。（六十多里）

liǎng dì de jù lí liù shí lǐ kāi wài.

The distance between those two places is over sixty miles.

前后 (qián hòu)

Except indicating location, "前后(qián hòu)" can also mean the period before or after a specific time. It is usually used after a specific number, event or activity. For example:

除了表示方位以外，还可表示比某一特定时间稍早或稍晚的一段时间。通常它跟在特定数字、事件或者活动之后。例如：

around the National Day (国庆前后- guó qìng qián hòu) 

around 2000 (2000年前后-èr líng líng líng nián qián hòu) 

around the time of the exam (考试前后- kǎo shì qián hòu)