Why is 100 wrong? ;)
Because you have to write it out in words ;)
The "correct answers" are written in grammatically incorrect English. "How many centimeters does a/one meter have?" would be more appropriate.
... and acceptable by Duolingo!
What's wrong with "how many centimeters are IN a meter?"
Is it wrong if I ask in this way : " How many centimeters are THERE in a meter?
no, i once experimented with a lot of combinations, and Duolingo will accept a lot of combinations.
For better understanding, what would the sentence look like if the English were, "A meter has how many centimeters?"
Um metro tem quantos centímetros?
Quantos centímetros um metro tem?
Tem quantos centímetros um metro?
Why can't i use there are
I suggest : "How many centimetres are there in a metre?" The Oxford Advanced Learners' Dictionary has "There are 100 centimetres in a metre."