Replace the question mark with the number below given a simple math problem.

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

what does the below math rebus puzzle mean?

Whats the next number in the below number sequence pattern.

In The 1st month of this year(the year 2013), I noticed that the date 13-1-13 (13 January 2013) is special.

This date is special as:

Date * Month = Year.

Can you figure out which year of this century has a maximum number of such dates?

You need to climb ten stairs. At every stair, you can either take one step up or you can jump two steps up.

In how many different ways you can climb 10 stairs?

An express train takes 3 seconds to enter the tunnel which is 1 km long.
If it is travelling at 120 km an hour, how long will it take to pass completely through the tunnel?

Next Number in the Series,

5, 16, 49, 104, ?

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