A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

I come in different shapes and sizes.
Parts of me are curved, other parts are straight.
You can put me anywhere you like,
but there is only one right place for me.
What am I?

I am a normal creature, but I have five hands. I can even have more but even then I will be considered normal.

Who am I?

Three brothers Jacob, John, and James live in Mexico City. The product of the ages of these brothers is 175. Jacob and John are twins. How old is James?

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

Who am I?

A pack of cards has 40 cards. You are blindfolded. Out of 40, 25 cards are facing down while 15 are facing up. You have been asked to divide this pack of cards into two decks - so that each deck contains an equal number of face-up cards. Remember, you are blindfolded.

How will you do it?

Two batsman each on 94 runs. Seven runs needed to win in last 3 balls. Both make 100*. How?

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different. How do you measure 45 minutes?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

Which statement is true out of the following?
One statement here is false.
Two statements here are false.
Three statements here are false.