The more of this there is, the less you see. What is it?

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

When it is alive we sing, when it is dead we clap our hands. What is it?

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

Two boys wish to cross a river. The only way to get to the other side is by boat, but that boat can only take one boy at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both boys manage to cross using the boat.

How?

Why Aeroplane windows are round?

Can you Find and name the hidden bird in the picture below ?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not-rounded numerals equals 24.

Take one out and scratch my head, I am now black but once was red. What am I?