# Examples for 8th grade - page 17

- The percentages in practice

If every tenth apple on the tree is rotten it can be expressed by percentages: 10% of the apples on the tree is rotten. Tell percent using the following information: a. in June rained 6 days b, increase worker pay 500 euros to 50 euros c, grabbed 21 fro - Gear

Two gears, fit into each other, has transfer 1:5. Centres of gears are spaced 28 cm. What are the radii of the gears? - Common chord

Two circles with radius 15 cm and 11 cm are intersect at two points. Its common chord is long 20 cm. What is the distance of the centers of these circles? - Map

Forest has an area of 36 ha. How much area is occupied by forest on the map at scale 1:5000? - 9.A

9.A to attend more than 20 students but fewer than 40 students. A third of the pupils wrote a math test to mark 1, the sixth to mark 2, the ninth to mark 3. No one gets mark 4. How many students of class 9.A wrote a test to mark 5? - Painters

One painter could paint a school for 7 days. The second one for 6 days. It was necessary to paint the school in two days. Next painter was invited and all worked together. How long would this painter painted the school itself? - Sisters

Sisters Hanka and Vera goes mostly tograndmother by bicycle. Journey took Hanka 30 minutes and Vera 20 minutes. How long will Vera catch up with Hanka when started from home five minutes later than Hanka? - Workman - shift

The worker produces 300 components per shift. How many components would be produced in 18 shift, if his performance gradually increased every shift by 3 components? - Moving

Vojta left the house at three o'clockat 4 km/h. After half hour later went from the same place Filip by bicycle at speed 25 km/h. How long take Tilip to catch up Vojta and how far from the house? - Base

Compute base of an isosceles triangle, with the arm a=9 cm and a height above the base h=6 cm. - Gutter

How much metal is needed for production 37 pieces of gutter pipes with the diameter 16 cm and length of 1 m? The plate bends add 7% of the material. - Coin

How many 20-cent coins must be put in a row that next 20-cent coins after them (above) rolled on it axis? - Tmp workers

Three temporary workers cleaned 60 m of walkway in 5 hours. How many meters of the walkway cleared seven volunteers for eight hours? - Cuboid - simple

Calculate the surface area and volume of a cuboid if a = 8 cm, b = 14 cm and c = 6 cm. - Class pairs

In a class of 34 students, including 14 boys and 20 girls. How many couples (heterosexual, boy-girl) we can create? By what formula? - Loan

If you take a bank loan $ 24000 and we want to repay after the year, we have to pay the total amount $ 24696/ What is the annual interest rate on this loan? - Painters

First painter painted fence himself for 12 hours, the second painter 3 hours sooner than first, and the third painters slowest up to 20 hours. How long took them paint fence if worked together? - Pyramid roof

? of area of the roof shaped regular tetrahedral pyramid with base edge 6 m and height of 3 m is already covered with roofing. How many square meters still needs to be covered? - Maximum area of rhombus

Calculate the interior angles at which equilateral rhombus has maximum area. - Sales off 2

Computer monitor sold for 8400 CZK in March. In April, dealer price decreased by 798 CZK. Calculate the percentage by which the price was reduced.

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