Logic Riddles

Question: When is 1500 plus 20 and 1600 minus 40 the same thing?

Question: What is the best way to stop a dog from barking in, and digging up the front yard?

Question: A king is on a cross-sea voyage and as soon as they get off of their boats he spots the most beautiful elephant he has ever seen. He decides to take it home, but first, he wants to know its weight.

The largest scale they brought only goes up to 50 pounds. The king demands that his smartest scholar must come up with a solution or pay the consequences. After several days he finally comes up with an answer.

Question: You have an 8 by 8 chess board that has two corner squares diagonal from each other removed. Is there any way to place 31 dominoes of size 2x1 to cover the remaining 62 spaces?

Question: There are two boys at an international math contest in December 2013; one is British and one is American. They both write their names, the date, and their answers on the paper. The only problem is that they both have the same name and the papers cannot be told apart.

What is the date?