# Mass - 8th grade (13y) - examples

1. CuSO4 mixture
How many grams of solid CuSO4 we have to add to 450g of 15% CuSO4 solution to produce a 25% solution?
2. Beer
After three 10° beers consumed in a short time there are 6.2 g of alcohol in 5 kg adult human blood. How much is it per mille?
3. Coffee
In stock are three kinds of branded coffee prices: I. kind......6.9 USD/kg II. kind......8.1 USD/kg III. kind.....10 USD/kg Mixing these three species in the ratio 8:6:3 create a mixture. What will be the price of 1100 grams of this mixture?
4. Sphere
Surface of the sphere is 2820 cm2, weight is 71 kg. What is its density?
5. 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 2.4 kg?
6. Vinegar 2
How many percentage of getvinegar solution, if we mix to 12 liters of 4.3% and 1 liters of 3.7% vinegar?
7. Density - simple example
Material of density of 762 kg/m3 occupies a container volume of 99 cm3. What is its mass?
8. Alcohol
How many 55% alcohol we need to pour into 14 liters 75% alcohol to get p3% of the alcohol? How many 65% alcohol we get?
9. Tare
Gross weight of shipment is 5188 kg and its tare is 5.6%. Calculate the net weight of the shipment.
10. Barrel of oil
Barrel of oil weighs 253 kg. When it mold 43% oil, weighed 159 kg. What is the mass of the empty barrel?
11. Cu thief
The thief stole 122 meters copper wire with cross-section area of 95 mm2. Calculate how much money gets in the scrap redemption, if redeemed copper for 5.5 eur/kg? The density of copper is 8.96 t/m3.
12. Air mass
What is the weight of the air in a classroom with dimensions 10 m × 0 m × 2.5 m ? The air density is 1.293 kg/m3.
13. Plastic pipe
Calculate weight of the plastic pipe with diameter d = 70 mm and length 380 cm if the wall thickness is 4 mm and the density of plastic is 1367 kg/m3.
14. Pump
What power has a pump output to move 4853 hl of water to a height of 31 m for 8 hours?
15. Pizza
Pizza with a diameter 50 cm have weight 559 g. What diameter will have a pizza weighing 855 g if it is make from the same cloth (same thickness....) and same decorated?
16. Hollow sphere
Calculate the weight of a hollow tungsten sphere (density 19.3 g/cm3), if the inner diameter is 14 cm and wall thickness is 3 mm.
17. Cube
The cube weighs 24 kg. How weight is cube of the same material, if its dimensions are 2-times smaller?
18. Metallurgical enterprise
Metallurgical company daily produces 318 tons of cast iron. How many tons of coke it burns to melt cast iron when 10 tons of cast consumes 6 tons of coke?
19. Canopy
Mr Peter has metal roof cone shape with a height of 101 cm and radius 189 cm over well. He needs paint the roof with anticorrosion. How many kg of color must he buy if the manufacturer specifies the consumption of 1 kg to 4.3 m2?
20. Solidarity
Imagine a word solidarity means that salt donation to the needy, who have neither the salt. If we take word solidarity has word base salt + gift (only in Slovakian language). Calculate how many kilos of salt sympathetic citizen "gives" government a year i

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