A class contains 38 pupils. Prove that within the class there will be at least 4 pupils born in the same month.
How, without any means of measurement, can you measure a length of 50 cm from a shoelace, whose length is \(2/3\) meters?
In the town of Ely, all the families have separate houses. On one fine day, each family moved into another, one of the houses house that used to be occupied by other families. They afterwards decided to paint all houses in red, blue or green colors in such a way that for each family the colour of the new and old houses would not match. Is this always possible to paint te houses in such a way, regardless of how families decided to move?
Find out the principles by which the numbers are depicted in the tables (shown in the figures below) and insert the missing number into the first table, and remove the extra number from the second table.
The Olympic gold-medalist Greyson, the silver-medalist Blackburn and bronze-medalist Reddick met in the club before training. “Pay attention,” remarked the black-haired one, “one of us is grey-haired, the other is red-haired, the third is black-haired. But none of us have the same colour hair as in our surnames. Funny, is not it?”. “You’re right,” the gold-medalist confirmed. What color is the hair of the silver-medalist?
On the street, four girls are talking in a circle: Anna, Kate, Jane and Nina. The girl in the green dress (not Anna and not Kate) stands between the girl in the blue dress and Nina. The girl in the white dress stands between the girl in the pink dress and Kate. What color dress was each girl wearing?
Find a two-digit number that is 5 times the sum of its digits.
Decipher the puzzle shown in the picture. Same letters correspond to same numbers, different letters to different numbers.
Three friends – Peter, Ryan and Sarah – are university students, each studying a different subject from one of the following: mathematics, physics or chemistry. If Peter is the mathematician then Sarah isn’t the physicist. If Ryan isn’t the physicist then Peter is the mathematician. If Sarah isn’t the mathematician then Ryan is the chemist. Can you determine which subject each of the friends is studying?
In the first pencil case, there is a lilac pen, a green pencil and a red eraser; in the second – a blue pen, a green pencil and a yellow eraser; in the third – a lilac pen, an orange pencil and a yellow eraser. The contents of these pencil cases are characterised by such a pattern: in every two of them exactly one pair of objects coincides in color and purpose. What should lie in the fourth pencil case, so that this pattern is preserved? (In each pencil case, there are exactly three objects: a pen, a pencil and an eraser.)