The world of cubes Difficulty level: In the "world of cubes", all constructions are made with grouped cubes. For example: Disregarding the different orientations, how many different ways can we group 4 cubes? Challenge 184 Painting the Faces of a Cube Challenge Index Next >> Challenge 186 Investigating the Sequence
Deciphering a barcode Difficulty level: A store uses short and long bars to store information about its products in the system. A short bar represents 0 (zero) and a long bar represents 1 (one). The bar to digit conversion codes are as follows: 11000 = 0 00011 = 1 00101 = 2 00110 = 3 01001 = 4 01010 = 5 01100 = 6 10001 = 7 10010 = 8 10100 = 9 Then observe the bar code below: Since the first bar on the left and 16 bars on the right are not part of the product code, what are the 9 digits that identify the product in this bar code?
Who is the big brother? Difficulty level: From three brothers, José, Adriano and Caio, it is known that either José is the oldest or Adriano is the youngest. It is also known that either Adriano is the oldest or Caio is the oldest. So who is the oldest and who is the youngest of the three brothers? Challenge 39 Calculator Keys Challenge Index Next >> Challenge 41 Solve the equation
What's the number? Difficulty level: Determine the smallest natural number whose: - division by 2 has remainder 1; - division by 3 has remainder 2; - division by 4 has remainder 3; - division by 5 has remainder 4; - division by 6 has remainder 5; - division 7 has remainder 0. Challenge 5 How much money? Challenge Index Next >> Challenge 7 Where are you?
Represent number 100 Difficulty level: Represent number 100 in three ways using only each of the 9 digits in their natural order (1, 2, 3, 4, 5, 6, 7, 8, 9) only using whole numbers. Challenge 74 Two Parents and Two Children Challenge Index Next >> Challenge 76 Great-Grandfather's Age
Ladder on the ship Difficulty level: Agrippino watched from a ship's wall as the tide rose. This wall hangs a ladder 8 meters long. The steps are 20 centimeters apart and the last one touches the water. The tide rises at a rate of 35 centimeters per hour. When will the first two steps be covered with water?
Saint Anthony miracle worker Difficulty level: Manoel had a certain amount of money and found it too small. As always complaining about life, one day found St. Anthony and made a proposal: - Oh dear St. Anthony, double the money I have, and I'll give you $ 10.00. So the saint did.
Two parents and two children Difficulty level: Two parents and two children went fishing. Each one fished a fish, and in all 3 fish were fished. How is this possible? Challenge 73 Number 6 with 3 equal digits Challenge table Next >> Challenge 75 Represent the number 100
The Farmer's Puzzle Difficulty Level: A farmer wanted to test his son's intelligence, called him, and said, "Son, take $ 100." I want you to buy 100 heads of cattle with that money. However, there can be no shortage or money left and it has to be 100 heads of exact cattle, and the price of each animal is: Bull: R $ 10,00 Cow: R $ 5,00 Calf: R $ 0,50 And one more thing: you have to bring at least one animal each.
Cooking the egg Difficulty level: You want to cook an egg in 2 minutes. However you only have 2 sand clocks, one 5 minutes and one 3 minutes. How could you put the egg to cook and take it out within 2 minutes? Challenge 77 The two watches Challenge index Next >> Challenge 79 The children of the couple Aguiar
Northeastern churros seller Difficulty level: Which of the following presents a contradiction? 1) Every seller of churros is northeastern and some northeastern is not seller of churros. 2) No churros seller is northeastern and some churros seller is not northeastern. 3) Some churros seller is northeastern and some churros seller is not northeastern.
Pancho Villa's Trip Difficulty Level: Pancho Villa travels from Acapulco to Guadalajara, traveling along a road at a constant speed. Passes a milestone (distance marker from Acapulco) that contains two digits. An hour later, it passes another milestone, containing the same two digits, but in reverse order.
Fire in the Rope Simply set fire to both ends of one string and to only one end of the other. When the fire completely consumes the first rope (within 30 minutes), set fire to the second end of the other rope. In another 15 minutes the second rope will be completely burned.