A girl and a boy are sitting on a long playground bench. Twenty other children approach them, and one by one sit down in-between two already sitting children until everybody is sitting comfortably on the bench. We call a boy “brave” if he sat between two girls, and we call a girl “brave” if she sat between two boys. How many boys and girls are “brave” if the boys and the girls who sit on the bench alternate?
The March Hare decided to amuse himself by playing with three red and five blue sticks of various lengths. He noticed that the total length of all red sticks is equal to 30sm, and the total length of all blue sticks is equal to 30sm as well. Can he cut the sticks in such a way that every stick of one colour had a pair stick of the other colour of the same lenghs?
Alice wants to mark 100 points on a plane by drawing it one by one, in such a way that no three points lay on one line, and at any moment while she marks the points down, the shape made up by the points has a symmetry line. Do you think it is possible?
You have two sticks and matchbox. Each stick takes exactly an hour to burn from one end to the other. The sticks are not identical and do not burn at a constant rate. As a result, two equal lengths of the stick would not necessarily burn in the same amount of time. How would you measure exactly 45 minutes by burning these sticks?
The text for this problem was originally typed in three different fonts and in three different colours. The original style is lost now, and Bella and Louise disagree on the following. Bella says that whatever the original font was it was always possible to choose three letters from the text such that all the three colours and all the three fonts were presented in that triple, and Louise does not think so. Who is right?
a) A bachelor student Peter haven’t slept properly for the last month. One of the reasons for that among many others was that every Monday at 3 p.m. he had a deadline for submitting his weekly calculus assignments. During the first month he counted six deadlines. Can it be the case or would you advise him to have more sleep?
(b) Once Peter checked the table with the assignment results he realized there were fewer Mondays in the last month. Is it possible there were only five Mondays?
Scrooge McDuck has 100 golden coins on his office table. He wants to distribute them into 10 piles so that no two piles contain the same amount of coins. And moreover, no matter how you divide any of the piles into two smaller piles among the resulting 11 piles there will be two with the same amount of coins. Sounds impossible? Try to find a suitable example. Scrooge spent a while on working out this question, maybe he will even give you a penny.
There are 36 parcels weighing 1 kg, 2 kg, 3 kg, ..., 36 kg. Today only three cars are in service. Each car has a capacity of 12 parcels. Can one distribute all packages between the cars in such a way that each vehicle has the same total weight of parcels?
a) In the context of Example 2 assume we have some number of parcels each weighing different amount of kilograms. We still have 3 identical cars of equal capacities (in numbers of packages) and we still want to distribute parcels in such a way that each car has the same total weight of parcels. Knowing that the number of parcels is not greater than 100 find the maximum and the minimum amounts of packages for which it is possible.
(b) Now we have 3 trucks so we do not really care about the sizes of parcels and their number. But yet we need to satisfy the condition of equal total weights of parcels in each vehicle. Can we do so if there are 27 packages weighing 1 kg, 2 kg, ..., 27 kg?
A battalion of soldiers was marching towards a captured city. Their progress was stopped by a wide river. Fortunately, close to the shore there were two boys sailing in a small boat. They escaped from the city and were eager to help the soldiers to cross the river. The only obstacle was that their boat could fit either two boys or one soldier. Taking into account one person was enough to handle that kind of boat (i.e. to sail from one shore to another) and the fact that on the next day the city was liberated so the boys could reunite with their families describe how the battalion was capable of crossing the river.