Good Riddles

Question: I was taking a plane to China and almost missed my flight. On my way to the terminal there were 7 other girls walking in the opposite direction. Each of these girls had 8 purses and each purse had 2 dogs.

How many in all were on the plane?

Question: I'm number three.
But I'm not a number.
I'm hot and cold at the same moment but not at the same time.
I'm number three.
But I'm not a number.

Who or what am I?

Question: Travel a mile and I will change.
Travel a million and I will end as I started.

What am I?

Question: You have 7 tennis balls that are all identical but one of them is slightly lighter than the others.

Using a balance scale and only two separate weightings, how can you find the light tennis ball?

Question: When you need me, you throw me away. But when you're done with me, you bring me back.

What am I?