Maths practice for 12-year-olds - page 66 of 355

Number of problems found: 7081

Cannon sound speed
A cannon fired at a distance of 2720 m from the observer. The sound of the shot was heard by the observer 8 seconds after the flash. Calculate the speed of sound propagation in the air if we assume that the observer saw the flash at the same time as the s
Egypt trip discount
A trip to Egypt was discounted by one-third of the price at the last minute. The discount was 5760 CZK. What was the original price of the tour?
Car average speed
A car drives for an hour on the highway at a speed of 100 km/h, then for half an hour at a speed of 80 km/h, and for another half hour in the field at a speed of 20 km/h. What track did he run together? What is the average speed of the car?
Fraction addition division
Add one-third to five-eighths and divide the result by the sum of the numbers five-quarters and two-thirds.
Number double reduced
It is necessary to determine the number whose double is reduced by 15 equals the number 5.
Puzzle wood density
The picture puzzle made of wooden cubes weighs 0.792 kg. One cube has an edge length of 4 cm and a weight of 33 grams. Find out how many cubes make up a puzzle and calculate the wood density in kg/m³.
Natural number sum
Calculate the sum of the squares of single-digit natural numbers less than 6
Bathroom tile count
The bathroom wall is 4m long. Her height is half. How many square meters of 10cm x 10cm square tiles will be needed to cover it?
The mesh
How many m² of mesh is used for fencing a square-shaped cage without a base with dimensions of 25m, 18m, 2.5m?
Resulting cross
From the corners of the square with a side length of 10 cm, we cut out small squares with a side length of 3 cm. What is the area of the resulting cross?
Diamond tile paving
How many diamond-shaped tiles with a side of 25 cm and a height of 20 cm are needed to pave a rectangular courtyard with sides of 30 m and 28 m if the joints represent 1/20 of the area?
Decorations - spherical
The glass Christmas decorations have the shape of a ball with a diameter of 8 cm. In a small family business, they produce 50,000 pieces a year. The entire surface of these balls is covered with glitter. 400 g of glitter is needed to cover an area of 1 m²
Body mass work
What was the body's mass when it moved along a path of 70 dm and did 1.4 kJ of work?
Diode forward resistance
What is the value of the resistance of the rectifier diode in the forward direction if the current IF = 5 A flows through it and the voltage between the anode UF = 820 mV?
Satellite runway speed
The satellite flies at a speed of 8 km/s. Will it fly down the runway in two seconds?
Number fivefold threefold
Find a number whose fivefold is 8 greater than threefold.
Cube tower ways
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.
Aja book pages
Little Aja planned to read the book, which has 120 pages, for 4 days. On the first day, she read a quarter of the whole book; on the second day, she had training and therefore only read two-fifteenths of the book; on the third day, she read seven-twentiet
Equation fraction solving
Calculate the equation and do the test. (x+6)/2 - (x+4)/4 = (2x+1)/3 – (x-4)/6
Car meeting location
Cars left two places 520 km apart simultaneously at speeds of 30 km/h and 50 km/h. Where and when will they meet?

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