Examples for 8th grade - page 75

  1. Mass
    tubes The thickness of a metallic tube is 1cm and its outer radius is 11cm. Find the mass of such 1m long tube, if the density of the metal is 7.5g per cubic cm.
  2. Numbers
    primes Write smallest three-digit number, which in division 5 and 7 gives the rest 2.
  3. Barrel 4
    sudy Barrel of water weighs 63 kg. After off 75% water, the weight of the barrel with water is 21 kg. How many kg weigh empty barrel and how many kgs water in it?
  4. Savings and retirement
    babky_1 The older sibling has saved 44% more euros than the youngest, which represents 22 euros. How many euros older brother has saved ?
  5. Equations
    p1110617 Solve following system of equations: 6(x+7)+4(y-5)=12 2(x+y)-3(-2x+4y)=-44
  6. Flowerbed
    garden_16 In the park there is a large circular flowerbed with a diameter of 12 m. Jakub circulated him ten times and the smaller Vojtoseven times. How many meters each went by and how many meters did Jakub run more than Vojta?
  7. Aunt
    teta Annie aunt is 35 years old, Annie is 14 years. For how many years will aunt have twice as many years as Annie?
  8. Joshka
    money-false Joshka had € 15. Mama took him 15%. How many had left?
  9. Simply equation
    img_reci Solve this equation for x: ?
  10. Rhombus 4
    diamond_shape Circumference of the rhombus is 44 cm, its height is 89 mm long. Calculate its content area.
  11. Motel
    motorest Three different dinners A, B, C are served in the motel. Three 20 members went to motel. Group 1 ordered dinners: A 20 members and their average dinner price in the group was CZK 200. From Group 2, they ordered a A: 10 persons, B 10 dinners, and their aver
  12. Password dalibor
    lock Kamila wants to change the password daliborZ by a) two consonants exchanged between themselves, b) changes one little vowel to such same great vowel c) makes this two changes. How many opportunities have a choice?
  13. Donuts
    buchty_1 In the dining room at one table sit Thomas, Filip and Martin. Together they eat 36 donuts. How many donuts eaten everyone, when Filip ate twice as much as Thomas and Martin even half over Filip?
  14. Buttons
    knofliky Shirt has 6 buttons, blouse has 4 buttons. All buttons are 176. Shirts and blouses are together 36. How many are the shirts and blouses?
  15. Unknown number 24
    numbs_6 f we add 20, we get 50% of its triple. What is this unknown number?
  16. Bath salts
    salt_1 Bath salt A weighs 900 grams and costs 36,40 CZK. Bath Salts B weighs 1000 grams, but costs 85 CZK. How much is a bath salt A cheaper than B one?
  17. Disc
    vysek.JPG Circumference of the disk is 78.5 cm. What is the circumference of the circular arc of 32° on the disc?
  18. Coins
    coins Denis and Zdeno together have 97 coins. If Denis had 4 coins less than he has now, the number of the coins would be in the ratio 14: 17. Determine the number of coins owned by Denis and Zdeno.
  19. Fuel economy
    car1_4 How many kilometers is sufficient petrol in the cylinder fuel tank with a diameter 40 cm and the base of tank length 1 m, when it is filled to 60% and if the car consume 15 liters per 100 km?
  20. Unknown number
    nums Identify unknown number which 1/5 is 40 greater than one tenth of that number.

Do you have an 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.