Solution:

Alex was one third of his father's age when he was 14. This goes back 31 years when his father was 42 years old.

Solution:

Let us denote the chocolates with p, q and r.
We can frame the following two equations now
p + q + r = 100 ------ (1)
5p + 3q + 0.5r = 100
or 10p + 6q + r = 200 ---- (2)

Now, 2*[(Eq. 2) - (Eq.1)]
9p + 5q = 100
from this equation'p' should be a multiple of 5
for p = 5 ; q = 11
for p = 10 ; q = 2
for p = 15 or more q becomes -ve

Therefore, the two possible answers are
p = 5, q = 11, r = 84
p = 10, q = 2, r = 88

Solution:

In the first observation, the time was 1:12. In the second observation, the time was 3:24.
Therefore, 2 hours and 12 minutes have elapsed.

Solution:

Actually, there are two series in the question. If you separate the alternate places, you will find that the first series is:
0, 1, 2, 3, 4
Where the digits are multiple of 1.

The second series is:
0, 2, 4, 6, __
Here, the digits are progressing with the multiples of 2.
Therefore, the next digit will be 8.

Solution:

102

Explanation:
The total number of animals in the zoo is one hundred and two i.e. thirty-four animals of each kind.

Since we already know that the number of each animal is same, each single deer, spider and cricket will have a total of eighteen legs.

Now, 612/18 = 34.

Therefore, total number of animals:
34 * 3 = 102

Solution:

It's a coin.

Solution:

The odd number is 820670987.

If you add up the first three digits of all the numbers, it adds up to 14 except for the third option i.e. 820670987.

Solution:

First shop: 80 pencils
80 * 5 paise = 400 paise = 4 rupees

Second Shop: 1 Pencil
1 * 1 = 1 Rupee

Third Shop: 19 pencils
19 * 5 rupees = 95 rupees

4 + 1 + 95 = 100 rupees.

Solution:

The South-East direction gets changed to North.

This is because by changing North-East into west, we are actually rotating the entire direction plane 135 degrees anticlockwise.

Solution:

The murderer is Soumya because 26 Jan is a national holiday in India and the municipality office remains closed.