Math practice for 13 year olds - page 330 of 414
Number of problems found: 8279
- Working time
If work is done in 16 days at a 10-hour shift, how many days will it be done at 8-hour shifts? - Tree height
A tree with an unknown height casts a shadow 18 m long at a time, while a two-meter pole casts a shadow of 2.4 m. How tall is the tree? - Seawater salt
By evaporating 15 kg of seawater, we get 517.5 g of salt. How much seawater do we need to obtain 3.45 kg of salt? - Cone
Calculate the volume of the rotating cone with a base radius of 26.3 cm and a side 38.4 cm long. - PIN attempts
How many attempts do I need to guess the 3-digit PIN to be sure I can guess it? - Pool inlets
At the swimming pool, they usually use three tributaries with the same power to fill the pool. Then the pool will fill in 5 hours. How many hours less would it take to fill the pool if they added 2 more inlets with the same capacity? - Two-digit numbers
Write all the two-digit numbers that can be composed of the digit 7,8,9 without repeating the digits. Which ones are divisible b) two, c) three d) six? - Original reduce
If we reduce the unknown number by 469, we get 65% of the original number. What is the original number? - Petrol consumption
Two identical cars use 12 l of petrol to cover 150 km. How much gasoline do 25 similar cars use per 1800 km? - Well digging cost
The width of the well with the masonry should be 1.8 m. How much will digging a well 16 m deep be paid if an average of 800 CZK is paid from meter cubic? - Dog food
The shelter buys a supply of food for 12 dogs for one week. How many days will this supply last if two more dogs are added to the shelter? - The tent
The tent shape of a regular quadrilateral pyramid has a base edge length of a = 2 m and a height of v = 1.8 m. If we have to add 7% of the seams, how many m² of cloth did we need to make the tent? How many m³ of air will be in the tent? - Cube walls
Find the volume and surface area of the cube if the area of one wall is 40 cm². - Five pumps
Three same pumps fill the tank with 50400 liters of diesel in 7 hours. How many liters of diesel will it take in 4 hours if we add two more of the same pumps and pump them the same way? How much more (or less) will they get if we add 2 of the same pumps a - Copper wire
What is the weight of 1000 m copper wire with a diameter of 5 mm when metric density p = 8.8 g/cm³? - Aquarium depth
The aquarium has the shape of a block with a length of 0.7 m and a width of 25 cm. It can hold 56 liters of water. How deep is the aquarium? - Pyramid four sides
A regular tetrahedral pyramid has a body height of 38 cm and a wall height of 42 cm. Calculate the surface area of the pyramid; the result is round to square centimeters. - RT perimeter
The leg of the rectangular triangle is 7 cm shorter than the second leg and 8 cm shorter than the hypotenuse. Calculate the triangle circumference. - Trapezium area
Given is a trapezoid ABCD with bases AB, CD. Let K be side AB's midpoint, and point L be side CD's midpoint. The area of triangle ALB is 15 cm2, and the area of triangle DKC is 10 cm². Calculate the area of trapezium ABCD. - Row strings
Find how many strings there are in the first row if there are 44 strings in the eighth row, and in each subsequent row, there are five more strings than in the previous row.
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