Logic puzzles to write on paper

Historical and technical insights about logic puzzles

NUMBER OF EGGS

Here is an enigma from The Canterbury Puzzles book by Henry Ernest Dudeney.
You have a certain number of eggs, you give half to a customer plus half an egg, of what you have left you give 1/3 plus 1/3 of egg to another customer, then sell 1/4 of the remaining plus 1/4 of egg to the third customer and finally give away 1/5 of the remaining plus 1/5 of the egg. The remaining eggs are given in equal parts to 13 friends. Of course, in all these steps you won't even break an egg.
What are the fewest eggs you need at the beginning?

CLOCK

For his birthday, Mario's friends give him a wall clock; could you tell how many times the minute and hour hands form a 90 degree angle in 12 hours?

WEIGHT SCALE. Mathematical

Look at the following picture, could you tell how many blue triangles you need to put in place of the question mark to keep the last weight scale in balance?

THE COINS GAME

Take thirteen one-euro coins and arrange them side by side to form a circle. Now, in turn, each of the two players remove one or two adjacent coins from the circle. The winner is whoever takes the last coin.
Could you find a way to always guarantee the victory to the player who starts the game second?

HOW MANY TIMES CAN YOU FOLD THE A4 SHEET?

All of us deal everyday with sheets of paper to take notes at school, to print on computers, to write a letter... But have you ever wondered what happens if we take one of these A4 sheets and start folding it?
Do you think it is possible to fold 20 times a 1/10 millimeter A4 sheet?
If yes, what would the thickness be? And what if, instead of 20 times, we fold it 60 times, how thick would it be?
Think about it but without trying!

THE PATH OF THE TURTLE

Look at the picture below consisting of a 42 squares lattice, imagine that a turtle should cover them all. The turtle is on a square and can move to another square, as long as it is close and has a whole side in common.
The picture also shows the position of the turtle when it is in the 11, 20 and 31 position.

RHIND MATHEMATICAL PAPYRUS ENIGMA

The Rhind Mathematical Papyrus is an ancient Egyptian document dating back to around 1650 b.C. and is also known as the Ahmes Papyrus, from the name of the scribe who transcribed it. It was bought in Luxor in 1850 by an antique dealer from Scotland, Henry Rhind, and is currently at the British Museum. In this 3 meters long and 33 cm high Papyrus are contained arithmetic, geometric, algebraic problems with solutions and fractional tables.
Here is a riddle inspired by the Papyrus.
One country consists of 7 houses, in each house 7 cats live and each cat catches 7 mice. Each mouse ate 7 corn on the cob and from each panicle, sowing the seeds, could be obtained 7 wheat sacks.
Could you tell the total of all?

HOW MANY TRIANGLES DO YOU SEE?

Do you have keen eyes to carefully observe the figure below?
Could you tell how many triangles are there?

They should be 12...

VINTAGE CARS

If two cars travel along a road, the first at a 30 km/h average speed and the second at 25 km/h and the first car arrives an hour before the second, would you know how long the road is?

THE ORCHARD

Mario has 4 orchards, the first orchard has 4 trees more than the second, the second orchard has 4 trees more than the third and the third has 4 trees more than the last one. Knowing also that the first orchard has twice as many fruit trees as the fourth, would you know how many fruit trees Mario has in his four orchards?

THE TWO HOURGLASSES

Mario owns two hourglasses at home, one in the kitchen and one in the living room, and he set up them at the same time; knowing that the hourglass in the kitchen indicates 15 but is 5 minutes slow every hour while the one in the room indicates 17 but is 5 minutes ahead every hour, would you know what time it is exactly and at what time the two hourglasses were set?

A LOVE LETTER

Lucilla wants the servant of the court to deliver a love letter to the young Enrico; for fear the servant would read it, she closes it in a small lockbox of which only she has the key. Even Enrico has a lockbox of which only he has the key. How can the two young fiancés exchange their love messages?

THE NUMERIC SERIES

Could you tell which number among 7-12-20 should be inserted instead of the question mark?
Resolve the logical series
1 and 6
8 and 9
10 and ?

SOURCE, SOLUTIONS + MANY OTHER RIDDLES / BRAIN TEASERS:

www.rompicapi.com