Can you find out what is missing?

1 3 5
2 4 ?

Hint: It's not six. Think out of the box.

Find the next number in the series

12, 20, 40, 72, 116, 172 ?

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?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

As a whole I am both
safe and secure.

Behead me and I become
a place of meeting.

Behead me again and I am
the partner of ready.

Restore me, and I become
the domain of beasts.

What am I?

One is to three as three is to five and five is to four and four is the magic number.
What is the pattern?

Find three whole, positive numbers that have the same answer when multiplied together as when added together.

Can you find the largest Three-digit number whose sum is 14 and whose square is less than 5,00,000?

100 prisoners are stuck in the prison in solitary cells. The warden of the prison got bored one day and offered them a challenge. He will put one prisoner per day, selected at random (a prisoner can be selected more than once), into a special room with a light bulb and a switch which controls the bulb. No other prisoners can see or control the light bulb. The prisoner in the special room can either turn on the bulb, turn off the bulb or do nothing. On any day, the prisoners can stop this process and say "Every prisoner has been in the special room at least once". If that happens to be true, all the prisoners will be set free. If it is false, then all the prisoners will be executed. The prisoners are given some time to discuss and figure out a solution. How do they ensure they all go free?