Examples for 8th grade - page 20

  1. Count of roots
    eggs How many solutions has equation x. y = 2531 with two unknowns on the set of natural numbers?
  2. Similarity n-gon
    podobnost 11-gones ABCDEFGHIJK and A'B'C'D'E'F'G'H'I'J'K' are similar. The area of 11-gon ABCDEFGHIJK is S1=254 cm2 and the diagonal length HG is 20 cm. Calculate area of the 11-gon A'B'C'D'E'F'G'H'I'J'K' if H'G' = 36 cm.
  3. Cone in cylinder
    cone_in_cylinder The cylinder is inscribed cone. Determine the ratio of the volume of cone and cylinder. The ratio express as a decimal number and as percentage.
  4. Two balls
    balls-inside-cylinder Two balls, one 8cm in radius and the other 6cm in radius, are placed in a cylindrical plastic container 10cm in radius. Find the volume of water necessary to cover them.
  5. Dog
    dog_and_man Man goes with a dog on a long walk 18 km from the house. Man is walking at speed 5.3 km/h and a dog that constantly running between house and man at 17.1 km/h. How many kilometers will run the dog when they reach their destination?
  6. Christmas Day
    stedryd In leap years was 53 Sundays. On what day of the week fell to Christmas Day?
  7. Rhombus HP
    rhombus3_1 Calculate area of the rhombus with height 98 mm and perimeter 20 mm.
  8. Insurance
    tornado The owner of the house is insured against natural disasters and pays 0.04% annually of the value of house 103 Eur. Calculate the value of the house. Calculate the probability of disaster, if you know that 42% of the insurance is to pay damages.
  9. Workers
    jumps Workers digging a jump pit in the school yard. Pit has a cuboid shape with a length 20 m, a width 20 dm and depth 36 cm. They excavate 0.4 cubic meters of soil an hour. How much time (hours and minutes) is need to the excavate this pit?
  10. Reservoir + water
    cuboid_water Reservoir completely filled with water weighs 13 kg. After pouring off three quarters of the amount of water weights 4 kg. Calculate the weight and volume of the reservoir.
  11. Height
    equilateral_triangle Calculate height of the equilateral triangle if its perimeter is 54?
  12. Electronics: Resistors in parallel
    resistors_1 From relation for calculating the resistance of parallel combination of resistors: ? Calculate the R, if R1 = 8kΩ a R2 = 18kΩ
  13. Sector
    vysec The perimeter of a circular sector with an angle 2 rad is 53 cm. Determine the radius of the circle from which the sector comes.
  14. Degrees to radians
    angle Convert magnitude of the angle α = 618°40'29" to radians:
  15. Concrete pipe
    concrete_pipe Concrete pipe is cylindrical with an inner diameter 130 cm and outer 142 cm. Calculate the surface of the concrete pipe, if it is 6 m long.
  16. Horizon
    lighthouse The top of a lighthouse is 12 m above the sea. How far away is an object which is just “on the horizon”? [Assume the earth is a sphere of radius 6378.1 km.]
  17. Circles
    SquareCircleSquare Area of circle inscribed in a square is 6. What is the area of a circle circumscribed around a square?
  18. Cathethus and the inscribed circle
    RightTriangleInradius In a right triangle is given one cathethus long 14 cm and the radius of the inscribed circle of 5 cm. Calculate the area of this right triangle.
  19. Task
    cube_1 I have homework. The cube has an edge 11 cm long and I must find wall and body diagonal.
  20. Salary
    500euro Clerk got to pay 1200 Euros in banknotes of 50 and 200 Eur. Total got 9 banknotes. How many was which?

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