Examples for 8th grade - page 85

Contract
8 employees complete the contract for 65 hours. After 17 hours, 3 employees had to leave for another job. How many more hours will the job on contract be fulfilled?
Square
Calculate the perimeter and the area of square with a diagonal length 30 cm.
Alcohol mixture
Three liters of 96 percent alcohol we set up a certain amount of distilled water to form a 54-percent alcohol. How many liters of distilled water were used?
Scale of map
James travels one kilometer in 12 minutes. The route walked for half an hour measured on the map 5 cm. Calculate how many kilometers James walked for half an hour. Find the scale of the map.
Trench
The trench is a four-sided prism. The cross section has a trapezoidal shape with basements of 4m and 6m, the length of the trench is 30m. What is the depth of the trench if we dig 60,000 l of soil.
Price saleoff
Shoes standing y euros. At first they were discounted by 12% and then 50% of the new amount. After this double cheapening the cost was exactly 22 euros. Determine the original price of shoes.
Comparing salaries
Spouses compared salaries. Mrs. Janka found that a 20% higher salary than Mr Jaroslav. Together earned € 1,430. How much they earn each of them?
Tailor master
There are less than 50m of textile in the tailoring workshop. When cutting on a blouse (consumption 1.5m), no textile is left. When using a cloth (consumption of 3.2m), no textile is left. How many meters of textile are in a tailor's workshop?
Chocolate roll
The cube of 5 cm chocolate roll weighs 30 g. How many calories will contain the same chocolate roller of a prism shape with a length of 0.5 m whose cross section is an isosceles trapezoid with bases 25 and 13 cm and legs 10 cm. You know that 100 g of this.
Two trains
There are two trains running the same distance. 1st train will travel it in 7 hours 21minutes. 2nd the train will travel 5 hours 57minutes and 34 seconds and it is 14 km/h faster than the first train. What are speeds of trains and how long is this railway
Two aircraft
Two planes fly to the airport. At some point, the first airplane is away from the airport 98 km and the second 138 km. The first aircraft flies at an average speed of 420 km/h, the second average speed is 360 km/h, while the tracks of both planes are perpe
Unknown number
Determine the unknown number, which double of its fourth square is equal the fifth its square.
PC disks
Peter has 45 disks in three colors. One-fifth of the disks are blue, red are twice more than the white. How much is blue, red and white disks?
Pyramid four sides
In a regular tetrahedral pyramid is a body height 38 cm and a wall height 42 cm. Calculate the surface area of the pyramid; the result round to square centimeters.
Resistance
Determine the resistance of the bulb with current 200 mA and is in regular lamp (230V).
Rhombus
If we increase the rhombus side by 2.4 cm; its perimeter is 20 cm. How long was the side of the rhombus?
Desribed circle to rectangle
Rectangle with sides 6 cm and 4 cm was circumscribed circle. What part of the content of the circle determined by the circumscribed circle occupies a rectangle? Express in perctentages(%).
Probably member
Look at the series 2,6,25,96,285, ? What number should come next?
Blueberries
Miko and Anton have a total of 1,580 blueberries. Miko and Anton have them in the ratio 2: 3. Determine how much each of them has.
Wall diagonal
Calculate the length of wall diagonal of the cube whose surface is 384 cm square.

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