Solution:

I am DAVID.

At the core I have 5
If we talk in roman numeric system, 5 = V

Similarly, 500 stands in the beginning and end
500 = D

I also include the first letter i.e. A and the first number i.e. I (in roman numeric system)

All of them combine to form DAVID.

Solution:

Read the question carefully again. New Year do falls after Christmas but that happens if two different years. The question is put up against the year 2050 and thus there will be 51 weeks and 2 days in between them as New Year will appear on 1 January 2050 and Christmas will happen on 25 December 2050.

Solution:

The ball will take infinite bounces before it is stopped. As per the question it will keep on bouncing half way up every time it hits the ground. But gravity will play its part at certain point of time which will make it stop.

Solution:

This quite an easy question and the answer is Rachel.

Since she is in the room, she is also a primate and being human, she is the smartest of all.

Solution:

Let us assume that all of them are standing on the X shore and they have to travel to the Y shore.

X = mother, first daughter, second daughter, father, first son, second son, maid and dog
Y = None

Maid and dog go first and maid returns back
X = mother, first daughter, second daughter, father, first son, second son and maid
Y = dog

Maid and first son go and maid returns with dog
X = mother, first daughter, second daughter, father, second son, maid and dog
Y = first son

Father and second son go and father returns back
X = mother, first daughter, second daughter, father, maid and dog
Y = first son and second son

Mother and father go and mother comes back
X = mother, first daughter, second daughter, maid and dog
Y = father, first son and second son

Maid and Dog go and Father returns back
X = mother, first daughter, second daughter and father
Y = first son, second son, maid and dog

Father and Mother go and mother comes back
X = mother, first daughter and second daughter
Y = father, first son, second son, maid and dog

Mother and first daughter go and maid comes back with dog
X = second daughter, maid and dog
Y = mother, first daughter, father, first son and second son

Maid and second daughter go and maid comes back
X = Maid and dog
Y = mother, first daughter, second daughter, father, first son and second son

Maid and dog go
X= none
Y = mother, first daughter, second daughter, father, first son, second son, maid and dog

Thus everyone has reached the other end.

Solution:

8

Explanation:
If you look carefully then you will see that five matches lay ahead of the lighter and five are visible in the reflection of the lighter. Out of those five, we can see three matches emerging away from the surface of the lighter but two remains just as a part of reflection. Thus the total number of matches are eight.

Solution:

54325

Explanation:

Consider 1 = 5
2 = 25
3 = 325
4 = 4325
Then 5 = 54325

See the pattern. With every digit, the previous numbers are added after that digit

So the next number in the series is 54325

Solution:

Cycle

Solution:

Adam and Eve were the only people without navel. As they were not born out of a mother, they never had umbilical cords and thus never had navels.

Solution:

Align the toothpicks to form TEN. Use one toothpick for each of the lines.