What has 13 hearts but no other organs?

Can you make the below equation true by using any three numbers from "1, 3, 5, 7, 9, 11, 13 and 15"?

( ) + ( ) + ( ) = 30

Two boys were admitted to a school. When the headmaster asks them about their parents, they tell him that they have same parents (father and mother). On further inquiry, it turns out that they both share the same date for their birthday.

"Are you twins," ask the headmaster.
"No," replies the boys.

Is it possible?

Find the smallest sentence with all the English alphabet.

The below given figure comprises of a pattern through which you can determine the missing letter. Can you push your mind to find the pattern and add the missing letter?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

A man fell off a smuggling boat into deep water. He could not swim and he was not wearing anything to keep him afloat. It took 30 minutes for the people on the boat to realize someone was missing. The missing man was rescued two hours later on the return trip. Why didn't he drown? Note:- He didn't know swimming, the sea was deep, and He wasn't holding anything

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

A certain street contains 100 buildings. They are numbered from 1 to 100. How many 9's are used in these numbers?