Reason - practice for 13 year olds - page 3 of 41
Number of problems found: 810
- Probability 81678
What is the probability of guessing a PIN code (4 numbers) if it contains only even numbers? - Probability 81637
We randomly select three different points from the vertices of a regular heptagon and connect them with line segments. The probability that the resulting triangle will be isosceles is equal to: (A) 1/3 (B) 2/5 (C) 3/5 (D) 4/7 - Restaurant 81584
Four students were paying the bill in the restaurant. Jan paid 7 rums and 20 beers, Adam 20 rums and 7 beers, Víťa 12 rums and 25 beers, and Dan 25 rums and 12 beers. Jan paid 20% less than Adam. By how much % less did Víťa pay than Dan? - Wreaths 81547
Eva paid €8.4 for three wreaths and five creams. Jana paid €15.6 for 9 wreaths and 7 creams. How many crowns will Jan pay for one wreath and one cream?
- Indistinguishable 81481
How many ways can a tower of five yellow and four blue cubes be built so that each yellow cube is adjacent to at least one other yellow cube? Yellow dice are indistinguishable, and so are blue dice. - Quadrilateral calc
The square ABCD is given. The midpoint of AB is E, the midpoint of BC is F, CD is G, and the midpoint of DA is H. Join AF, BG, CH, and DE. Inside the square (approximately in the middle), the intersections of these line segments form a quadrilateral. Calc - Probability 81446
What is the probability that each digit is different in a five-digit number? - Several resistors
We have a box with the same resistors, so all of them have a resistance value of 200 ohms. Draw the connection of several resistors so that the resulting resistance is: a) 100 b) 120 (only 4 resistors) - Quadrilateral 81097
The quadrilateral ABCD is symmetrical about the diagonal AC. The length of AC is 12 cm, the length of BC is 6 cm, and the interior angle at vertex B is right. points E and F are given on the sides AB, and AD so that the triangle ECF is equilateral. Determ
- Thanks 81022
Pavla is 2x older than Irena. Four years ago, Pavla was 6 times older than Irena was then. In how many years will the ages of Pavla and Irena be in the ratio of 4:3? Thanks - Multiply 80797
When I multiply two equal natural numbers, I get the same result as when I add them together. Which ones are they? - Three-digit 80768
Nikola had one three-digit and one two-digit number written in her notebook. Each of these numbers was made up of different digits. The difference in Nicole's numbers was 976. What was their sum? - Parallelogram 80761
Construct a parallelogram ABCD if a=5 cm, height to side a is 5 cm, and angle ASB = 120 degrees. S is the intersection of the diagonals. - Single-digit 80674
There are cows, ducks, and geese on the farm. They have a total of 126 legs. Ducks are 3 more than houses. And there are 20 cows. If we count all the animals, we have to divide them by the number three, and we should get a single-digit number.
- Grandchildren 80639
The average age of the grandfather, grandmother, and their five grandchildren is 26 years. The average age of the grandchildren themselves is 7 years. Grandma is a year younger than grandpa. How old is grandma? - Nightmares 80568
At the dream market, she offered the Sphinx to a traveler for four dreams, seven illusions, two naps, and one nightmare. Another has seven dreams, four illusions, four naps, and two nightmares. The Sphinx always measures the same for all travelers. How ma - Chessboard 80533
How many ways can one white and one black square be selected on an 8x8 chessboard if the selected squares cannot lie in the same row or column? - Smallest 80368
What is the smallest whole number to replace the known x for: 9> x/3> 4. - Five-digit 80104
How many different five-digit numbers with different digits can be made from the digits 0, 2, 4, 6, 7, 8, and 9? How many of them are divisible by 4? How many of them are divisible by 10? How many of them are even?
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