Ratio - 8th grade (13y) - 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.
Area of square garden is 6/7 of triangle garden with sides 96 m, 60 m and 60 m. How many meters of fencing need to fence a square garden?
- Forestry workers
In the forest is employed 63 laborers planting trees in nurseries. For 11 hour work day would end job in 43 days. After 14 days, 22 laborers go forth. How many days is needed to complete a planting trees in nurseries by others, if they will work 15 hours
Gross wage was 1762 USD including 22% bonus. How many USD were bonuses?
Route is long 203 km and the first day first regiment went at an average speed 20 km/h and journey back 19 km/h. The second day went second regiment same route at an average speed 18 km/h there and back. Which regiment will take route longer?
- Motion problem
From Košíc to Bratislavy go car at speed 76 km/h. From Bratislavy to Košíc go another car at speed 60 km/h. How many minutes before the meeting will be cars 22 km away?
Mr. Radoslav calculated that excavation for a water connection dig for 10 days. His friend would take 7 days. Radoslav worked 3 days alone. Then his friend came to help and started on the other end. On what day since the beginning of excavation they met?
After three 10° beers consumed in a short time there are 5.2 g of alcohol in 6 kg adult human blood. How much is it per mille?
One meter of the textile were discounted by 2.4 USD. Now 6 m of textile cost as before 3 m. Calculate the old and new price of 1 m of the textile.
If you go at speed 6.1 km/h, you come to the station 51 minutes after leaving train. If you go by bike to the station at speed 17 km/h, you come to the station 43 minutes before its departure. How far is the train station?
Calculate how many promiles river Vltava average falls, if on section long 695 km flowing water from 1601 m AMSL to 183 m AMSL.
Calculate how many average minutes a year is the web server is unavailable, the availability is 99.99%.
The cuboid has a surface area 3380 cm2, the length of its edges are in the ratio 4:3:1. Calculate the volume of the cuboid.
- Gimli Glider
Aircraft Boeing 767 lose both engines at 45000 feet. The plane captain maintain optimum gliding conditions. Every minute, lose 2080 feet and maintain constant speed 196 knots. Calculate how long takes to plane from engines failure to hit ground. Calculate
Swimming pool is long 110 m and 30 m wide. The plan of the city is shown as a rectangle with area 13200 cm2. What scale is the city plan?
Calculate fixed annual personnel costs of operating monorail line 106 km long if every 5 km is station, which serve three people - one dispatcher and two switchman in 3-shift operation. Consider the average salary of the employee 847 €.
The areas of the two circles are in the ratio 1:15. The larger circle has diameter 25. Calculate the radius of the smaller circle.
- Eiffel Tower
Eiffel Tower in Paris is 300 meters high, is made of steel. Its weight is 8000 tons. How tall is the tower model made of the same material, if it weigh is 4.8 kg?
Fire tank has cuboid shape with a rectangular floor measuring 14.5 m × 9.8 m. Water depth is 2 m. Water was pumped from the tank into barrels with a capacity of 3 hl. How many barrels were used, if the water level in the tank fallen 12 cm? Write
Determine the number of all positive integers less than 2937474 if each is divisible by 11, 23, 17. What is its sum?
- Density - simple example
Material of density of 1278 kg/m3 occupies a container volume of 80 cm3. What is its mass?
Do you have interesting mathematical example that you can't solve it? Enter it
and we can try to solve it.