Math practice for 13 year olds - page 311 of 413
Number of problems found: 8254
- Train speed
A train running at 20 m/s passes by an observer in 5 seconds. Another train, 250 m long, runs on the adjacent track in the opposite direction. Find the speed of the second train. - Book profit
How much more expensive is it for the owner to sell a book he bought in an antiquarian book for half the price if he sells it for two-thirds of the original price? - Three colors 2/3
Marek has balls of three colors. Two-thirds of the balls are green, 2/7 are blue, and one ball is yellow. How many balls does Marek have? - Class students
3/4 of the class went skiing. Of those who stayed home, 1/3 fell ill, and the remaining 6 were at a math camp. How many students does the class have? - Volume of an apple
How many apples will fit in a box measuring 20 cm × 50 cm × 25 cm? - Triangle arm
There is an isosceles triangle with a circumference of 36 cm, and the height at the base is 12 cm long. Calculate the length of the arm of a given triangle. - Percent to number
To increase that number by 5 percent, we need to multiply it by: - Triangle perimeter
The area of an equilateral triangle is 81√3 cm². Calculate its circumference. - The pipe
The pipe is 1.5 m long. Its outer diameter is 60 cm, inner diameter is 52 cm. Calculate the pipe's weight if the material's density from which it is made is 2 g/cm³. Please round the results to whole kilograms. - The cast
The cast in the body of a regular quadrilateral pyramid with a base edge 60 cm long and 5 cm high is made of a material with a density of 7.8 g/cm cubic. Calculate its weight. - If we
If we increase the unknown number by 4%, we get 780. Determine the unknown number. - Dog chase
While hunting, the dog sees a hare in the bushes 20 meters ahead. The hare starts running, and the dog starts chasing it simultaneously. A hare runs at a speed of 39 km/h, and a dog at 45 km/h. In how many seconds does the dog catch up with the hare? - Cylinder hole
A cylinder-shaped hole with a diameter of 12 cm is drilled into a block of height 50 cm with a square base with an edge length of 20 cm. The axis of this opening passes through the center of the base of the cuboid. Calculate the volume and surface area of - Ice and water
We want to cover a rectangular rink with dimensions of 55 m and 25 m with a 4 cm thick layer of ice. How many liters of water do we need if freezing water increases its volume by 10%? - Rhombus and diagonals
The rhombus area is 150 cm2, and the ratio of the diagonals is 3:4. Calculate the length of its height. - Material transport
Two trucks were supposed to load the building materials in 10 days. After 6 days of work, the first car broke down, and the second one carried building materials for another 9 days. How many days would the first and second cars take the building materials - Apples 2
Dried apples contain 15% water. Fresh apples contain 80% water. How many kilograms of apples must we buy to get 3 kg of dried apples? - Diagonal of square
Calculate the side of a square when its diagonal is 10 cm. - Christmas
Father said, " Exactly after 56 hours, we will sit down at the Christmas Eve table." How was it, and what time was it, when Father said this sentence? They sat at the Christmas Eve table at exactly 6 PM. - Tower model
The tower's height is 300 meters, and its weight is 8000 tons. How high is the model of the tower's weight of 1 kg? (State the result in centimeters). The model is made from exactly the same material as the original no numbers need to be rounded. A result
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