Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

How many letters are in the alphabet?

I make two people out of one. What am I?

I am white when I am dirty, and black when I am clean. What am I?

I know a nine-letter word having only one vowel.
Do you ?

A man started to town with a fox, a goose, and a sack of corn. He came to a stream which he had to cross in a tiny boat. He could only take one across at a time. He could not leave the fox alone with the goose or the goose alone with the corn. How did he get them all safely over the stream?

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?

What has one letter and starts with an E?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?