# Examples for 7th grade (seventh) - page 28

1. Percentage of waste In a square plate with side 75 cm we cut 4 same circles. Calculate the percentage of waste.
2. News From 28 students buy magazine 10 The economist students, 10 Pravda students and 18 students don't buy any of these magazines. How many students buy both magazines?
3. 6 regular polygon It is given 6 side regular polygon whose side is 5 cm. Calculate its content area. Compare how many more cm2 (square centimeters) has a circle in which is inscribed the 6-gon.
4. Stairs Between adjacent levels are 15 stairs. If step will be 1.2 cm lower there would be 16 stairs. What is the stair height?
5. Nine balls Imagine that you have exactly the same appearance nine balls of which one has a greater mass than the other. You have isosceles weights. Post a procedure as you would using a weights to discover heavier balls. How many measurements at least you have to do?
6. Cars motion From point A car start at the speed of 90 km/h. Against it departs from the point B at the same time another car at 60 km/h. For how long and where they met if the distance between A and B is 180 km?
7. Water level The glass container has a cuboid shape with dimensions of the bottom 24 cm and 12 cm. The height of water is 26 cm. Calculate the volume of the body, which are sunk into the water if the water level rise by 3 cm.
8. Two trains Two trains go at each other. First at speed 40 km/h and the second at speed 60 km/h. At what distance will be 30 minutes before they will meet?
9. Roots Calculate the square root of these numbers:
10. Slope Calculate the slope of a line that intersects points (-84,41) and (-76,-32).
11. Bank deposit Ms Jana after the withdraw amount of 2,500 euros after year saving in bank. What was her deposit if the interest rate was 2.5% p.a..
12. The dam The water reservoir is filled with first tributary for 25 hours second tributary for 35 hours. Some time were both inlets open, then a second tributary closed and the tank was filled in four hours. What time water flowed from both tributaries? (Expressed i
13. Bulbs In the box are 6 bulbs with power 75 W, 14 bulbs with power 40 W and 15 with 60 W. Calculate probability that a randomly selected bulb is:
14. Wood Wood contains 12% water. 1 m3 of wood weighs 650 kg. How many liters of water it contains?
15. The cylindrical container The container has a cylindrical shape the base diameter 0.8 meters has a content area of the base is equal to the content area of the shell. How many full liters of water can be poured maximally into the container?
16. Map scale Garden has on plan on a scale of 1: 150 width 22 cm and length 35 cm. What is the real area of the garden?
17. Square room What is the size of the smallest square room, which can pave with tiles with dimensions 55 cm and 45 cm? How many such tiles is needed?
18. Water reservoir The water reservoir is filled with one pump for 4 days by the second one for 9 days. Outlet can drain tank in 12 days. How long take fill the reservoir if both pumps are running and not closed outlet channel.
19. Shoes Peter decided to measure shoes size of his three friends. Measured accurately and wrote as follows: Venda and Jenda together 52 cm Jenda and Zdenda together 58 cm Zdenda and Venda together 54 cm a) How long measures Vendy, Jenda and Zdenda shoes together
20. Pair They have together 39 years - he has 2 times as she was when he was equal as she has today ....

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