Ratio + multiplication - examples

On solving problems and tasks with proportionally we recommend hint rule of three. Rule of three (proportionality) help solve examples of direct and inverse proportionality. Three members makes possible to calculate the fourth - unknown member.

  1. Chocolate
    cokolada Ivan bought 7 same chocolates for 28 Eur. How many euros he pay for 21 chocolates?
  2. Forestry workers
    forestry_workers In the forest is employed 64 laborers planting trees in nurseries. For 8 hour work day would end job in 35 days. After 12 days, 20 laborers go forth. How many days is needed to complete a planting trees in nurseries by others, if they will work 9 hours a
  3. Bonus
    moeny Gross wage was 1430 USD including 23% bonus. How many USD were bonuses?
  4. Motion problem
    dragway From Martina to Bratislavy go car at speed 76 km/h. From Bratislavy to Martina go another car at speed 53 km/h. How many minutes before the meeting will be cars 19 km away?
  5. Cyclist
    cyclist_2 A cyclist passes 88 km in 4 hours. How many kilometers he pass in 8 hours?
  6. Store
    pave One meter of the textile were discounted by 2 USD. Now 9 m of textile cost as before 8 m. Calculate the old and new price of 1 m of the textile.
  7. Motion
    cyclist_1 If you go at speed 5.1 km/h, you come to the station 37 minutes after leaving train. If you go by bike to the station at speed 28 km/h, you come to the station 38 minutes before its departure. How far is the train station?
  8. Server
    p_pro Calculate how many average minutes a year is the web server is unavailable, the availability is 99.99%.
  9. Blood
    krv In human body the blood is about 7.2% body weight. How many kilograms of blood is in the human body with weight 93 kg?
  10. Chickens
    chickens 2 chickens give 2 eggs in 2 days. How many eggs can give 8 chickens for 8 days?
  11. Observer
    ohrada The observer sees straight fence 100 m long in 30° view angle. From one end of the fence is 153 m. How far is it from the another end of the fence?
  12. ŽSR
    luzianky Calculate fixed annual personnel costs of operating monorail line 118 km long if every 5 km is station, which serve three people - one dispatcher and two switchman in 4-shift operation. Consider the average salary of the employee 885 €.
  13. Youth track
    tunel Youth track from Hronská Dúbrava to Banská Štiavnica which announced cancellation attracted considerable media attention and public opposition, has cost 6.3 euro per capita and revenue 13 cents per capita. Calculate size of subsidies to trip group of 10.
  14. School trip
    school_trip School trip cost 184.8 USD for one class (28 students). How much would cost a trip for two classes? (both classes together have 56 students)
  15. Numbers
    ten Determine the number of all positive integers less than 4183444 if each is divisible by 29, 7, 17. What is its sum?
  16. Cats
    cats Two cats caught two mice in two days. How many mouses will catch 6 cats for 6 days?
  17. Daily average
    weather_forecast Calculate the average temperature during the day, when 13 hours was 22 °C and 11 hours was 17 °C.
  18. Gear wheels
    gear Two gear wheels, which fit together have number of teeth z1=128 and z2=94. Calculate the speed of the first wheel, if the second wheel rotates 1507 revolutions per minute.
  19. Profitable bank deposit 2012
    eurocoins Calculate the value of what money lose creditor with a deposit € 9500 for 4 years if the entire duration are interest 2.6% p.a. and tax on interest is 19% and annual inflation is 3.7% (Calculate what you will lose if you leave money lying idle at negative
  20. Discount
    sales_discount Product has been discounted twice by 15%. What is the total discount given?

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