When we see 2 but call 10?

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

Decipher

yyyy u r, yyyyy u b, i c u r y+y 4 ? by sharks. How would you survive?

In the picture given below, can you find out which digit will take place of the question mark?

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

why number 8549176320 is one of a kind?

You have $100 with you and you have to buy 100 balls with it. 100 is the exact figure and you can't go below or above the numbers and you have to use the entire $100. If there is no kind of tax applied how many of each of the following balls will you be able to buy:

Green Balls costing $6
Yellow Balls costing $3
Black Balls costing $0.10

Now, how many of each must you buy to fulfil the condition given?

I start and end with 500 and carry a 5 in my heart. But I require the first letter and the first number to be complete. I am the name of a King.

Who am I ?

What runs around the whole yard without moving?

Divide 110 into two parts so that one will be 150 per cent of the other. What are the 2 numbers?