Kids Riddles

Question: You have found a mutant algae that doubles in size every hour. It takes 18 hours for one algae plant to take up half of a certain lake.

How long would it take for two of these plants to take up half of the same lake?

Question: I can go up a chimney down but not down a chimney up?

What am I?

Question: I wasn't born a horse,
and I never fly.
Yet sometimes I still soar,
right into the sky.
I often contain breath,
and yet I never die.
Sometimes I am torn,
but I never sigh.
Often, with ambition, I aspire,
and go till I can go no higher.
Then, like many men, so great,
I sink into a low state.
What am I?

Question: A man has 3 children and half of them are girls, how is this possible?

Question: I am a cave full of bones,
and the house of a worm.

What am I?