Can you find the dog hidden in a group of pandas?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

Prove that twice of ten is the same as twice of eleven.

What is a word made up of 4 letters, yet is also made up of 3. Sometimes is written with 9 letters, and then with 4. Rarely consists of 6, and never is written with 5.

In the addition below, all digits have been replaced by letters. Equal letters represent equal digits and different letters represent different digits.
ABCABA
BBDCAA
ABEABB
ABDBAA
------- +
AAFGBDH
What does the complete addition look like in digits?

I am lying and I always lie. Tell me whether I am lying or telling the truth.

What number divided by 4 is the same as that number minus 4?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.