"I want to buy a bag of rice."
I looked up all of the vocabulary before beginning the lesson and "袋", one of the new words listed for this lesson, is also a classifier for "bag" according to Wiktionary: https://en.wiktionary.org/wiki/%E8%A2%8B. (That source uses "一袋米" as an example.)
My answer, which used "袋" instead of "包", was nevertheless rejected. Seems like it should be accepted.
They can be synonyms for soft rectangular sacks that serve as a packet, e.g. rice sacks. But they also differ in many places. The intuitive impression in brief: 包 is more of “wrapper, pack, packet”; 袋 is more of “pouch, pocket” (usually made with soft material and a unsealable/sealable opening, e.g. plastic bags, paper bags, rice bags).
It sounds like 袋 would also cover typical uses of English "sack" too then.
Yeah. When I hear 一包米, a firm rectangular plastic sack appears in my mind — it is mainly the shape and softness that makes me feel okay to use 包.
Hmph. I put "我想要买一包米“ and it said my answer was incorrect. I'm pretty sure that can be considered a correct answer.
Your sentence means. I should like to buy. This changes the meaning of the sentence as it is intended that you want to buy a bag of rice and not that you should like to buy one (but does not want at this moment).
"Should like to" is so utterly archaic in English that I don't even know for sure what it means. I only know it from movies made before I was born, and I'm fifty.
But I think "should" in that sense means the same as "would" as most people speak English today.
It means a bag of rice, typically bought in 10kgs or more. Corn would be 玉米 yùmǐ.
Are you thinking of 爆米花 Bào mǐhuā which is popcorn?
I thinks he confused it with 苞米, which means "maize" in some dialects (how did he even know this word?).
It is correct. 想 and 想要 express the desire. 要 is very ambiguous and it can mean both 想要 (desire, want), 需要 (need, want) and 将要 (will, be going to), and other meanings.
Imagine a packet (other than a lunchbox) of cooked rice and where you can buy it. :-|
Your sentence would be just I want to buy ricesacks. Here it is asked for a specific amount of ricebags so you MUST give a number and measure word.
Under some conditions, we do just omit 一, so this sentence can be a possible translation. However this can be ambiguous as Brillenschnecke said, so using a complete sentence is better.
Could it mean "sack of rice" though? (I see it's also dialectal for "corn".)
Yes, it can be short for 一包米 (“a sack/bag of rice”). Such expressions are very common. But, before you get to know the restrictions in Putonghua, better use this form only: Verb + Quantity/Determiner + Classifier + Object (i.e. do not use it without the verb). For example, you should not leave out the characters in brackets: 我(那)包米 “the bag of rice of mine”, 地上(那)包米 “… on the ground”, 关于(那)包米 “about …”.