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

What does it mean?

Most people think of me as money. But when they find me in the water, they won’t get any money out of me. What am I?

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?

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

There is a wide field of corn. A goose finds its way into the field and starts running. Can you find out till which point the goose can run into the field?

Can you find out the next digit in the following series ?

0, 0, 1, 3, 2, 6, 3, 9, 4, 12, 5, ?

A mathematics teacher took exams for his students. Out of the total students, 25% passed both the tests included in the exam. However, only 42% were able to clear the first test.

Can you find out the percentage of those students who passed the first test and also passed the second test?

What is the value of 1/2 of 2/3 of 3/4 of 4/5 of 5/6 of 6/7 of 7/8 of 8/9 of 9/10 of 1000?