Problem No. 7. Coins on a table

There are 7 coins laid on a table with the heads up, and 30 coins laid with the tails up. Each coin has a head side and a tail side. How can you split the coins in two piles, with your eyes closed, so that the piles have the same number of coins with the tails up?

Teacher tip

Use logic puzzles at your classes to increase the motivation and to exercise the flexibility in mathematical thinking.

Problem No. 6. Clock hands revisited

How many times in a day the clock hands will form the same angle as the angle at 7.30?

Student tip

For a hint use Problem No. 3.

Problem No. 5. Missing numbers

Here is a 5 x 5 table filed with numbers according to some rule. What are the missing numbers?

Parent tip

Exploring patterns with your children can be a fun way to spend some quality time together.

Problem No. 4. Airplane fly

The travel by plane from Paris,France to New York City, USA, takes about 8 hours. If a passenger starts his journey from Paris at 7.30 pm local time, when is he supposed to arrive at New York City, local time?

Teacher tip

Problems with an extra-mathematical knowledge are suitable to demonstrate the application of math and its interdisciplinary character. Here, the students should be familiar with or should first learn about time zones.

Problem No. 3. Clock hands

It is 7.30 now. How much time will it pass until the clock hands form the same angle again?

Student tip

Suppose that minute and hour hands move at a constant velocity each.

Problem No. 2. Book

Ann usually has the following problem at 7.30 in the mornings: She wakes up and wants to continue reading the book that she had read the night before, but the lamp she uses for reading has depleted batteries and she does have neither spare batteries nor another lamp nearby. But, she always manages to solve the problem very quickly, without leaving either the room or the bed, and continues to read the book. How does she do it?

Parent tip

Suitable for family time, especially with younger children to exercise their listening skills.

Problem No. 1. Digital Clock

It is 7.30 now. How long should we wait until the digital clock uses the same digits to display the time?

Teacher tip

Good recreational problem for a "warm up" activity at the beginning of the class.