In the figure, an electrical circuit is drawn. In the middle of the circuit a infinitely long metal bar is placed indicated with the grey circle. In this bar, an oscillating magnetic field is induced by a coil which is attached somewhere to the bar. Two resistors are located in the circuit with values R1 and R2. The alternating voltages V1 and V2 are being measured with two perfect alternating voltages meters. What is the relation between the two voltages V1 and V2? a) V1 : V2 = R2 : R1 b) V1 : V2 = 1 : 1 c) V1 : V2 = R1 : R2 d) V1 = V2 = 0 e) something different.

Mr. House would like to visit his old friend Mr. Street, who is living in the main street of a small village. The main steet has 50 houses divided into two blocks and numbered from 1 to 20 and 21 to 50. Since Mr. House has forgotten the number, he asks it from a passer-by, who replies "Just try to guess it." Mr. House likes playing games and asks three questions:

1. In which block is it?
2. Is the number even?
3. Is it a square?

After Mr. House has received the answers, he says: "I'm still doubting, but if you'll tell me whether the digit 4 is in the number, I will know the answer!". Then Mr. House runs to the building in which he thinks his friend is living. He rings, a man opens the door and it turns out that he's wrong. The man starts laughing and tells Mr. House: "Your advisor is the biggest liar of the whole village. He never speaks the truth!". Mr. House thinks for a moment and says "Thanks, now I know the real address of Mr. Street".
What is the adress of Mr. Street?

In a suburb three new houses all have to be connected to a gas (red), water (blue) and electricity (green) supply. All houses should get their own gas, water and electricity connection. Furthermore no connections may cross each other. Because of the danger of stealing, no connections are laid below a house. In the figure on the right-hand side the situation is sketched. The red squares are the houses, the circles the point from which the connections should go to the houses. Why is it impossible to lay down all connections in such a way that no connection crosses another connection?