Mathematical Olympiad - practice problems
MO tasks are not easy, even for adults. At the same time, we believe that the right solution, which is here published almost on one click will serve as the inspiration.Do not be discouraged if you did not discover the right solution. Experiment, sketching, "play" with the problem. Sometimes it helps to look into a book and find out similar problems resolved. Sometimes help three days pause, and then you found the right solution.
Direction: Solve each problem carefully and show your solution in each item.
Number of problems found: 176
- MO Z7 2025
Adela and Susan ate plums. On the first day, Adela ate three quarters of what Susan ate that day. On the second day, Susan ate three halves of what Adela ate that day. Together, they ate 31 plums over the two days, and each girl ate the entire number of p - Digit sum MO Z9-I-4
Determine whether it is possible to add a single-digit number to the number with the digit sum of 2024 so that the resulting number has the digit sum of 74. - Semicircles
In a rectangle with sides of 4cm and 8cm, there are two different semicircles, each of which has its endpoints at its adjacent vertices and touches the opposite side. Construct a square such that its two vertices lie on one semicircle, the remaining two o - Circumferences 83111
Péta composed several planar shapes from mutually congruent triangles. The circumferences of the first three are 8 cm, 11.4 cm, and 14.7 cm, respectively. Determine the perimeter of the fourth shape. - Characters 82998
Adam wrote the following sum with five secret adders: a + bb + ccc + dddd + eeeee. He revealed that the characters "a, b, c, d, e" represent the different digits 1, 2, 3, 4, and 5 and that the resulting sum is divisible by 11. Which is the smallest and wh - Determine 82724
A right triangle has an area of 36 cm². A square is placed in it so that two sides of the square are parts of two sides of a triangle, and one vertex of the square is in a third of the longest side. Determine the area of this square. - Quadrilateral 82616
Triangle ABC is divided into line segments. Lines DE and AB are parallel. Triangles CDH, CHI, CIE, and FIH have the same area, namely 8 dm². Find the area of quadrilateral AFHD.
- Two-digit 82521 Karel had to multiply two two-digit numbers. Out of care, he changed the order of the digits in one of the factors and got a product that was 4,248 less than the correct result. What is the correct result? How much should Karl have earned?
- Gardening
In the gardening community, Mr. Strawberry had 16 liters of water in his barrel. Neighbor Malina had three times more water in his barrel than Mr. Strawberry. It started to rain and the same amount of water rained into both barrels. After the rain, Mr. Ma - Department 82388
Last year, there were 30 more boys than girls in our scout troop. This year, the number of children in the ward increased by 10%, while the number of boys increased by 5% and the number of girls increased by 20%. How many children do we have in the depart - Subtract 82333 I think of three numbers; when I add them, I get 16; when I subtract the third from the sum of the first two numbers, I get 10; when I subtract the second from the sum of the first and third numbers, I get 8. Which numbers do I think?
- 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 - Respectively 81293
The figure shows the squares ABCD, EFCA, CHCE, and IJHE. Points S, B, F, and G are, respectively, the centers of these squares. Line segment AC is 1 cm long. Determine the area of triangle IJS. Please help... - Intersection 81017
There are also two equilateral triangles ABC, and BDE, such that the size of the angle ABD is greater than 120° and less than 180° points C and E lie in the same half-plane defined by the line AD. The intersection of CD and AE is marked F. Determine the s - Respectively 80982
The vertices of the square ABCD are joined by the broken line DEFGHB. The smaller angles at the vertices E, F, G, and H are right angles, and the line segments DE, EF, FG, GH, and HB measure 6 cm, 4 cm, 4 cm, 1 cm, and 2 cm, respectively. Determine the ar
- Double-digit 80970 Eva thought of two natural numbers. She first added these correctly, then subtracted them correctly. In both cases, she got a double-digit result. The product of the resulting two-digit numbers was 645. Which numbers did Eva think of? Please, what is this
- SKMO Petra had written natural numbers from 1 to 9. She added two of these numbers, deleted them, and wrote the resulting sum instead of the summaries. She thus had eight numbers written down, which she managed to divide into two groups with the same product.
- 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? - Originally 80757
There were 45 sheep and several shepherds in the meadow. After half of the shepherds and a third of the sheep left the meadow, the remaining shepherds and sheep had a total of 126 legs. All sheep and all shepherds usually had leg counts. how many shepherd - 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?
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