What four weights can be used to balance from 1 to 30 pounds?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

A person is found murdered in his Chamber. When the crime scene is investigated, the Investigator find out that there is a calendar on which the victim has written a few numbers with his blood. The numbers are 4, 11, 11 and 4.

There are four suspects in the murder, John, Jacob, Anna and Lee. Can you find out who is the murderer?

What does this say?

XLR8

Can you tell a 3D object that has just two surfaces?

Below, you can see some coding:
January = 1017
February = 628
March = 1335
April = 145
May = 1353
June = 1064
July = 1074
August = 186

Now deciphering the way it has been coded, can you find out how September will be coded?

I am Huge on Sunday and Saturday.
I am small from Tuesday to Thursday.
I do not exist on Monday and Friday.
Who am I?

Complete the table series riddle by finding the number that can replace "??".