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 picture(rebus) riddle means ?

Solve below rebus puzzle?

John was running from 40 thieves. John has got 3 gold boxes which weigh as 4kg, 2kg, and 1kg respectively. A witty man asked John to stay with him for seven days in exchange for 1kg gold per day. John needs to stay there for seven days and also do not want to give the witty man any advance. How can John pay for his seven days stay?

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?

Mr Black, Mr Gray, and Mr White are fighting in a truel. They each get a gun and take turns shooting at each other until only one person is left. Mr Black, who hits his shot 1/3 of the time, gets to shoot first. Mr Gray, who hits his shot 2/3 of the time, gets to shoot next, assuming he is still alive. Mr White, who hits his shot all the time, shoots next, assuming he is also alive. The cycle repeats. If you are Mr Black, where should you shoot first for the highest chance of survival?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?

Decode this picture on T-Shirt and tell what it says ?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

What can you hold in your right hand, but never in your left hand?