Math practice for 13 year olds - page 69 of 422
Number of problems found: 8427
- Passenger train
At 9:15 AM, a passenger train passes the station at a speed of 75 km/h. At 10 o'clock, an express train passes through the same station in the same direction at a speed of 120 km/h. Both trains arrive at the same destination station at the same time. a) a - Probability 81964
Calculate the probability of the event that you sit in seats 1 to 30 in the cinema at: a) seat marked with a prime number b) seat marked with an even number c) a seat marked with a number divisible by 3 or 4 - Staircase 81963
How long is the staircase railing with 17 steps if the step is 32 cm deep and 14.5 cm high? The last step does not count. - Dimensions 81957
How many bricks are needed to build a wall that is 12 m long, 1.6 m high, and 47 cm wide if the dimensions of the brick are 30 x 15 x 7.5 cm and 5% of the wall volume is mortar? - Propagation 81955
A plane flying at 612 km/h speed sent a sound signal. In front of the aircraft (in the direction of flight), there is a fixed object at a distance of 3 km, from which the sound is reflected back to the plane. How long will it take the pilot to hear the ec - We randomly
We randomly select a three-digit number. What is the probability that the number 8 occurs at most once in its notation? - Competition 81952
All three team members took turns fulfilling the competition task without delay. The first member used up 30% of the total competition time. The second needed 10 minutes more than the first, and only 10 minutes remained for the third. What % of the total - Calculate 81950
The tangent of the angle formed by the adjacent sides of the triangle ABC (side a=29 m, b = 40 m) equals 1.05. Calculate the area of that triangle. - Inscribed cube
A cube is inscribed in a sphere with a radius of 27 cm. Calculate its volume and surface area. - Small density cube
Calculate the mass of a cube with an edge of 15 cm made of oak wood with a density of ρ = 800 kg/m³. - Increased 81943
The mobile was increased by a quarter of the original price and then again by a quarter of the new price. How much did the mobile cost if its final price was 125 euros? - Consumption 81941
The car consumes up to 16 l in the city, but on a longer trip, the consumption drops to 10 l? 500 km per month in the city and 1650 km outside the city. What is the consumption of a car per 100 km? - Calculate 81939
The block surface is 5,632 m². The lengths of the edges are in the ratio 1: 2 : 3. Calculate the volume of the cuboid. - Increased 81938
We increased the side of the square by 12% from the original 15cm. For a, what was the perimeter and area of the new square? By what percent did the perimeter and area increase? - Cantilevers 81937
Calculate a prism's volume and surface area with a base of a right triangle with cantilevers of length 40 and 43 cm. The height of the prism is 60 cm. - Cube-shaped 81931
A ball with a diameter of 10 cm is in a cube-shaped box with an edge of 10 cm. What percentage of the box does the ball fill? - Subtracting 81925
Three horses will eat 36 kg of oats in two days. How many kilograms do 5 horses need for 4 days? Help yourself by adding or subtracting. - Foresters 81919
Foresters planted 2,440 saplings in three days. On the second day, they planted 20% more saplings than on the first day, and on the third day, 15% less than on the first day. How many saplings did the foresters plant each day? - Observatory's dome
In our city, they decided to reconstruct the observatory's dome and cover it with sheet metal. At least how many square meters of sheet metal will they need if the dome is in the shape of a hemisphere with a diameter of 6m? - Percentage 81914
The carpenter worked on a rotary cylinder with a base radius of 2.5 dm and a height of 2 dm. He reduced the radius by 1 cm by uniform grinding, and the height of the cylinder was preserved. Calculate the percentage by which the volume of the cylinder has
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