Examples for 8th grade - page 82

  1. Alcohol mixture
    roztoky_1 From 55% and 80% alcohol we have to produce 0.2 kg of 60% alcohol. How many of them do we use in solution?
  2. Regular quadrilateral pyramid
    pyramid_3 Find the volume and surface of a regular quadrilateral pyramid if the bottom edge is 45 cm long and the pyramid height is 7 cm.
  3. Inequation
    inequalities Solve the inequation: 5k - (7k - 1)≤ 2/5 . (5-k)-2
  4. Water wessel
    karafa The vessel containing water has a weight 19 kg. After pouring half the water its weigth 11 kg. What is the weight of the empty vessel?
  5. Kite
    drake_1 John a kite, which is diamond shaped. Its diagonals are 60 cm long and 90 cm long. Calculate: a) the diamond side b) how much paper John needs to make a kite if he needs paper on both sides and needs 5% of the paper for bending.
  6. Repair company
    servis The company repairs cars. The first day repair half of the contract second day, the half of the rest and third day 8 residue cars. How many total cars company repaired?
  7. Banknotes
    ducat $ 1390 was collected. How much was in $20 notes and how many in $50 notes in that order? How many solutions exists?
  8. The plan
    zber Students have collected 48 kg of paper which is 16% of the plan. How many kg of paper still have to collect to fulfill the plan?
  9. Internal angles
    triangle_5 Find the internal angles of the triangle ABC if the angle at the vertex C is twice the angle at the B and the angle at the vertex B is 4 degrees smaller than the angle at the vertex A.
  10. Apples 2
    jablka_6 Dried apples contain 15% water. Fresh apples contain 80% water. How many kg of apples we need buy in order to get 3 kg of dried apples?
  11. Threesome
    3friends_1 Dana, Dalibor and Michael have a combined 57 years. Dana is five years older than Dalibor, but Dana is five years younger than Michael. Determine how old is Dana, Dalibor and Michael.
  12. Diagonals of a rhombus
    rhombus-diagonals_1 One of the diagonals of a rhombus is twice as the other. If the sum of the lengths of the diagonals is 24, find the area of the rhombus.
  13. Diamond perimeter
    Diamond_1000 Calculate the diamond circumference which area is 288 cm square and one diagonal has a size of 124 cm.
  14. Fertilizer
    luka_1 Meadow with an area of 1,500 square meters was fertilized with 12 kg of urea. Urea contains 45% nitrogen. How much nitrogen accounted per 1 m2?
  15. Four integers
    tiles2 Fnd four consecutive integers so that the product of the first two is 70 times smaller than the product of the next two.
  16. Collection
    maliny_1 John has collected half a bucket of raspberries in 45 minutes, Eva collects the whole bucket in an hour. How many minutes it would take to fill a bucket if the two children work together?
  17. Fit ball
    fitball What is the size of the surface of Gymball (FIT - ball) with a diameter of 65 cm?
  18. The swing
    houpacka To swing the two girls. Aneta weight 45 kg and Simon 35 kg weight. How far should sit Simon from the middle of swing so it is balanced, if we know that Aneta is sitting at distance 1,5m? How far are girls sitting apart?
  19. Metal pyramid
    jehlan_5 Find the weight of a regular quadrilateral pyramid with a 5 cm length and 6,5 cm body height is made from material with density g/cm3.
  20. Circular ring
    mezikruzi Square with area 16 centimeters square are inscribed circle k1 and described circle k2. Calculate the area of circular ring, which circles k1, k2 form.

Do you have interesting mathematical example that you can't solve it? Enter it and we can try to solve it.

To this e-mail address we will reply solution; solved examples are also published here. Please enter e-mail correctly and check whether you don't have a full mailbox.