Using Only Five 5's and any mathematical operator make sum as 37

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.

What does this mean?

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A worker is to perform work for you for seven straight days. In return for his work, you will pay him 1/7th of a bar of gold per day. The worker requires a daily payment of 1/7th of the bar of gold. What and where are the fewest number of cuts to the bar of gold that will allow you to pay him 1/7th each day?

What happened when the wheel was invented?

I can sizzle like bacon,
I am made with an egg,
I have plenty of backbone, but lack a good leg,
I peel layers like onions, but still remain whole,
I can be long, like a flagpole, yet fit in a hole.

Decode the below four famous ciphers:

8P of the SS
1M of the E
1S of the SS
60M in 1H

Below rebus represent famous DiCaprio movie. Can you name it?

What does this rebus means ?

What is so fragile that saying its name breaks it?