What has 13 hearts but no other organs?

A landlord calls both of his sons and tells them that their horses will now decide who will transfer the inheritance. He tells them to race along the land till the end and the one whose horse will be slower will win and be the heir to all the property.

Both of them keep wandering for days but to no result. Then they ask a wise man regarding it. The man advises them on the matter after which they jump on the horses and race as fast as they can till the end. Why did they do it?

What did the wise man say?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

Andrew’s doctor gives him three pills and tells him to take one every half hour. How much time will have passed by the time Andrew’s taken all three pills?

Can you replace the question mark with the correct number?

Find the next number in the series below

21 32 54 87 131 ?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

I am a five-letter word under you,
Remove the first letter and I am above you,
Remove the second as well and I am around you.

Who am I?

There is a box full of marbles,
all but two are blue,
all but two are green,
and all but two are red.

How many marbles are in the box?

What have one eye but still cannot see?