All Puzzles

My goal is to have $12. If I save $1 a month then it will take me 12 months to save $12. If I save $2 a month then it will take me 6 months to save $12. What if I saved $1.50 each month? How many months would it take me to save $12?

John walks over a railway-bridge. At the moment that he is just ten meters away from the middle of the bridge, he hears a train coming from behind. At that moment, the train, which travels at a speed of 90 km/h, is exactly as far away from the bridge as the bridge measures in length. Without hesitation, John rushes straight towards the train to get off the bridge. In this way, he misses the train by just four meters! If John had rushed exactly as fast in the other direction, the train would have hit him eight meters before the end of the bridge.

What is the length of the railway-bridge?

Every day, John takes the train to travel from his work back to Mexico City, his place of residence. Usually, he arrives at the station of Mexico at six o’clock, and exactly at that moment, his wife picks him up by car. Yesterday evening, John took an earlier train, without informing his wife, and therefore he already was at the station of Mexico at five o’clock. He decided to walk part of the way to meet his wife. When he met the car with his wife, he drove home with her. In this way, they were home ten minutes earlier than normal. John’s wife always drives the entire way between home and station at the same constant speed.

How long did John walk yesterday evening?