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

A seven-year-old kid challenged his classmates that he can make the number one disappear by adding something to it.

How can he do that?

When you stop to look, you can always see me. But if you try to touch me, you can never feel me. Although you walk towards me, I remain the same distance from you. What am I?

You see me once in June, twice in November, and not at all in May. What am I?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

Two girls were born to the same mother, on the same day, at the same time, in the same month and year and yet they're not twins. How can this be ?

If 2 workers can complete painting 2 walls in exactly 2 hours.

How many workers would be needed to paint 18 walls in 6 hours?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

what's the probability of getting a king or a queen from a pack of 52 cards?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?