Best riddles for teens

I eat other animals. I have a big mouth. I am green. I live in the water. Who am I?

Thirty white horses on a red hill. First they champ, Then they stamp, Then they stand still. Who are they?

What do you get if you add 3 to 300 five times?

What has a neck but no head?

When you have me, you feel like sharing me. But, if you do share me, you don't have me. What am i?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth I am dissolved into air. What am I?

Where does Valentine’s Day come after Easter?

I sleep when you are awake, I am awake when you fall asleep. I can fly but no feathers to aid my flight. What am I?

It can fill a room without occupying space. What is that?

How many seconds are there in a year?