# Examples for 8th grade - page 60

1. Isosceles trapezoid
Calculate the content of an isosceles trapezoid whose bases are at ratio 5:3, the arm is 6cm long and it is 4cm high.
2. The deposit
Deposit has been placed for one year at an annual rate of 4.5%. After the added interst amount rose to € 2,612.5. Determine initial deposit.
3. Hexagon = 8 parts
Divide the regular hexagon into eight equal parts.
4. Classroom
In a class are 32 pupils. Boys are 8 less than girls. How many boys and girls are in the classroom?
5. Millionaire
Mr. Smith have gone withdraw from bank saving interest € 1,500. How big was his initial deposit if the annual interest rate is 1.5%?
6. Calcium and citality
The daily dose of calcium obtained using 0.75 liters of milk and 60 grams of cheese. A/ At the morning I drank half a liter of milk. How much cheese I must eatto eat a daily dose of calcium? b / I ate 50 grams of cheese, how much milk I must drink? c /.
7. Cube containers
Two containers shaped of cube with edges of 0.7 m and 0.9 m replace a single cube so that it has the same volume as the original two together. What is the length of the edges of the new cube?
8. The book
If one day you read p pages, you will read the book 24 days. If you read each day 10 pages more, you would read a book in 16 days. How many pages have the book?
9. Solutions
How much 60% solution and how much 35% solution is needed to create 100 l of 40% solution?
10. Supplementary angles
One of the supplementary angles are three times larger than the other. What size is larger of supplementary angles?
11. Trapezoid
How long are the trapezoid bases with area 24 cm2 and height 3 cm. One base is 3 times longer than the shorter.
12. Painters
Five painters painting the fence for eight days. How many days over will take work if paint the fence only four decorators?
13. Circle and rectangle
A rectangle with sides of 11.7 cm and 175 mm is described by circle. What is its length? Calculate the content area of the circle described by this circle.
14. Uranium ore
Uranium ore contains 0.2% of pure uranium and pure uranium contains 0.07% of fissile uranium. How many grams of fissile uranium contains 2800 ton of uranium ore?
15. Earth's surface
The greater part of the earth's surface (r = 6371 km) is covered by oceans; their area is approximately 71% of the Earth's surface. What is the approximate area of the land?
16. Salt
Sea water containing 5% salt. How many kg of fresh water necessary to pour into 40 kg of sea water so that the salinity fell to 2%?
17. Sugar
Sugar factory produced 127 tons of sugar in 1 day at 14% sugar content . How many tons of pure beet sugar factory processed in 1 day?
18. Salt
1 t of sea water contains 25 kg of salt. How many tons of seawater must be evaporated to obtain 2 q of salt?
19. Outer angles
The outer angle of the triangle ABC at the A vertex is 71°40 ' outer angle at the vertx B is 136°50'. What size has the inner triangle angle at the vertex C?
20. Surface area of cylinder
Determine the lateral surface of the rotary cylinder which is circumscribed cube with edge length 5 cm.

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