Was there a race?
- I had a strange dream last night.
- Tell me all about it.
- I went to see car racing.
- I didn’t know you cared for cars.
- Before the race the cars were parked in a square fashion.
- What do you mean?
- There were equally many cars each column and row.
- You mean that there were a square numbers of cars?
- I guess you could put it like that.
- Then what?
- After the race they were parked in a rectangular shape with 5 more in each row than in the square lineup.
- How many were there in each column?
- You tell me!
The Royal Spanish Mathematics Society is 100 years old this year. The newspaper El País celebrates this with a math problem every week. The problem above is, in essence, one of them. Here is a video presenting the problem (in Spanish).