### Illusion

A security camera, taking pictures each half a second, films a cyclist going by. In the film, the cyclist appears to go forward while the wheels appear to go backwards. Why?

### Walk and Ride

How far have these students walked by the time the teacher's car reaches them after their bus broke down?

### John's Train Is on Time

A train leaves on time. After it has gone 8 miles (at 33mph) the driver looks at his watch and sees that the hour hand is exactly over the minute hand. When did the train leave the station?

# Speedy Sidney

##### Stage: 3 Challenge Level:

The problem can be solved by considering the relative speed of the trains.

The speed of approach of the trains is 125 km/h on a 100 km track, so they will collide after a time 100/125 = 4/5 hour. Sidney flies at 100 km/h for 4/5 hour so he flies 80 km.

Finally, if Sidney were to fly exactly 100 km, the relative speed of the trains would be 100 km/h, provided Sidney was continuing to fly at 100 km/h. OR ..... there is another way - do you have any suggestions?

We received the correct solutions from: Stephen Smith(South Greenhoe Middle School).