How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

When it's bad luck to meet a black cat?

Two natural numbers have a sum of less than 100 and are greater than one.

John knows the product of the numbers and Jacob knows the sum of numbers.

The following conversation takes place between them:
John: 'I am not aware of those numbers.'
Jacob: 'I knew you wouldn't be. I am not aware myself.'
John: 'Now I know them!'
Jacob: 'Now I know them, too!'

What are the two numbers?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

In a school, there are four subjects. Seventy percent of students study English, seventy five percent of students study Science, eighty five percent of students study Mathematics and eighty percent of students study Spanish.

Can you calculate the percentage of students that study all four subjects?

Can you find the odd number in the following five choices?

1) 482636
2) 259807
3) 865195
4) 104739
5) 391744

By including only four matchsticks in below picture, you have to make "Four Triangles And Two Squares"

What time is it when an elephant sits on a fence?

If you're 8 feet away from a door and with each move you advance half the distance to the door. How many moves will it take to reach the door?

In a football game, Christina defeated Teresa by 2 - 0 but no man from either side scored. How can this be possible?