Our product and our sum always give the same answer. Who are we?

I am the fastest animal but cannot climb the tree. What am I?

What is next number in the pattern below:

131 517 192 123 ?

The average age of 10 members of a committee is the same as it was 4 years ago, because an old member has been replaced by a young member. Find how much younger is the new member ?

Nodes are shown below and you need to connect them based on the following rule: Every node can be connected to the number of nodes inside them, i.e. the first node there is a value of 1 which indicates that the first node can connect to exactly one node only.Can you do it?

It's pretty hard to give up.
If you remove a part of it, you will be left with a bit.
Even if you remove another part, the bit still remains.
Remove one more and it still remains.

What is it?

Baseball bat and ball cost $100. If the bat cost $99 more than the ball, what is the cost of each?

Buy me, smell me or deliver me, I do not change.

Who am I?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?