Why is a river so rich ?

Find the missing number in the series below

13 -21 34 -55 ? -144

You have to fill the below given grid in a manner that every row and column contains the digits 1 to 6. Also, make sure that the squares that are connected with each other must contains the same digit.

How many triangles are there in the picture below?

Can you name three consecutive days without using the words Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday?

You find yourself in a strange place guarded by two guards.One of the guard always say truth while other always lies.You don't know the identity of the two.You can ask only one question to go out from there. What should you ask?

Christina is practising her dance steps along with her friends. In a particular sequence, all of them form a row. At that point, Niharika is standing in the 4th position from either end of the row.
Can you find out how many girls are practising together?

Count the number of triangles in the picture below:

My location can be determined by the below rebus.
So where am i ?

John walks into the daily grocery shop and steals a $100 bill from the shop. An hour later John returns to the shop and buys some daily products for $40. John pays the owner the $100 bill and therefore the owner returns him $60.

How much money did the owner lose?