Question

A man was 50 years old in 2000 but 40 years old in 2010. How is this possible?

Answer 1

Let me tell u that this is not the question of mathematics its of IQ. The answer is that it would have been2000b.c(before Christ) when he was 50 years old.And b.c is counted oppositely than that of a.d which is in present years.b.c means the years before the birth of Jesus Christ.

Answer 2

Well, I agree with Kunal that this answer is of IQ !
Anyways heading back to the answer,

It is relatively simple because you didn't mention that the person was 50 years old in 2000 B.C. or A.D.

And that's what the answer is !
The man was 50 years old in 2000 B.C. so obviously he would be 40 years old in 2010 B.C.

The BCs and ADs makes a lot of difference! Isn't it ? Keep moving !