Percentage above 100 I am stuck on helping my nine-year old on a percentage question. She has quite a few questions of this form, however but I don't know the method of solving them. Here is one of the questions:
Question: 

Yesterday $200$ flights left Heathrow airport. $21$ of these flights were to Edinburgh.
  What percentage is this?

Possible Answers:
(A): $105.00\%$
(B): $10.50\%$
(C): $1.05\%$
(D): $21.00\%$
(E): $1050.00\%$  
Can someone provide an explanation for this particular question so I can assist her on solving the others?
Update:
I apologize that I did not include what we have done thus far. Her and I are quite competent on working out $100\%$ questions. There was the following question which was fine for her: 

"There are $25$ cars on the road and $18$ of them are red.
  What percentage is this?

She simplified the ratio down to get $72\%$, which is the correct answer!
I think the problem is that I have no idea how to do anything about $100\%$. So when $200\%$ comes up I am lost on this. Any explanation would be appreciated. She currently does a lot of simplifying questions with percentages and I would assume this was similar but the books I have do not really explain anything above $100\%$ and I can't afford new books at the moment for her.

We want to find $x$ so that $\frac{21}{200}=\frac{x}{100}$
Multiplying by $100$ on both sides yields:
$x=\frac{100\cdot21}{200}=\frac{21}{2}=10.5$
