Why do we preferably have round manhole covers and not square ones?

The two towns are exactly 100 km apart. John leaves City A driving at 30 km/hr and Jacob leaves City B half an hour later driving at 60 km/hr. Who will be closer to City A when they meet?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

It is raining today at 11:59 am. What is the probability of sunny weather after 72 hours?

Can you fill the blank with the correct number?

6 30 870 756030 _____

There was a man he lives in a hotel each morning he presses the first floor button each evening if there is a person in the elevator he asks him to press the 10 floor button if there is no one in the elevator he takes the stairs why.

One is to three as three is to five and five is to four and four is the magic number.
What is the pattern?

If a zookeeper had 100 pairs of animals in her zoo, and two pairs of babies are born for each one of the original animals, then (sadly) 23 animals don’t survive, how many animals do you have left in total?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?