What is the next number in this series?

4,12,84,3612....

Spot 5 differences in two Christmas tree below:

Can you solve the below geography rebus by decoding the below rebus ?

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

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?

Which Travels Faster? Solve below famous picture riddle:

What has many keys but can’t open a single lock?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

What occurs twice in a week, once in a year but never in a day?

What can go up a chimney down, but can’t go down a chimney up?