Solution:

This happened because the last kid took the whole container with him in which the burger was present.

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:

36 Quadrilaterals

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.

Solution:

Yes, this is possible. The doctor is the wife and the mother.

Solution:

9

Explanation:
5 cartons for large boxes = 5 * 6 = 30 boxes
4 cartons for small boxes = 4 * 9 = 36 boxes

He will need 9 cartons to place 66 boxes.

Solution:

The man is 84 years old.
The son is 49 years old.
The grandson is 7 years old.

Solution:

Both of them were able to cross the river because they were standing on the opposite sides of the river.