# 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
Juan bought 9 same chocolates for 9 Eur. How many euros he pay for 29 chocolates?
2. Forestry workers
In the forest is employed 43 laborers planting trees in nurseries. For 6 hour work day would end job in 35 days. After 11 days, 8 laborers go forth? How many days is needed to complete planting trees in nurseries by others, if they will work 10 hours a da
3. Bonus
Gross wage was 1430 USD including 23% bonus. How many USD were bonuses?
4. Motion problem
From Levíc to Košíc go car at speed 81 km/h. From Košíc to Levíc go another car at speed 69 km/h. How many minutes before the meeting will be cars 27 km away?
5. Cyclist
A cyclist passes 88 km in 4 hours. How many kilometers he pass in 8 hours?
6. Store
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
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
Calculate how many average minutes a year is the web server is unavailable, the availability is 99.99%.
9. Blood
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
2 chickens give 2 eggs in 2 days. How many eggs can give 8 chickens for 8 days?
11. Observer
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
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
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 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
Determine the number of all positive integers less than 4183444 if each is divisible by 29, 7, 17. What is its sum?
16. Cats
Two cats caught two mice in two days. How many mouses will catch 6 cats for 6 days?
17. Daily average
Calculate the average temperature during the day, when 13 hours was 22 °C and 11 hours was 17 °C.
18. Gear wheels
Two gear wheels, which fit together have number of teeth z1=120 and z2=80. Calculate the speed of the first wheel, if the second wheel rotates 1669 revolutions per minute.
19. Profitable bank deposit 2012
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
Product has been discounted twice by 15%. What is the total discount given?

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