# Examples for 8th grade - page 31

- Cube and water

How many liters of water can fit into a cube with an edge length of 0.11 m? - Swing

A child weighing 12 kg is sitting on a swing at a distance of 130 cm from the axis of rotation. How far away from the axis of rotation (center) must sit down his mother weighs 57 kg if she wants to be swing in balance? - Sprayers

The vineyard can be sprayed first sprayer in 5 hours and with the second in 7 hours. How long would it take if we use sprayers both at once? - Cuboids in cube

How many cuboids with dimensions of 6 cm, 8 cm and 12 cm can fit into a cube with side 96 centimeters? - Gasholder

The gasholder has spherical shape with a diameter 23 m. How many m^{3}can hold in? - Bath

In the bath is 30 liters of hot water. Then added 38 liters of cold water at temperature of 17 °C decreased temperature of water to 48 °C. What was the initial temperature of the hot water? - Paul and Honza

Honza went to chat on a bike without a break 3.0 hours. Paul the same way without breaks 30 minutes longer. The difference between the speeds of the two boys was the one kilometer per hour. How fast was Paul, if you know that the speed of the boys did not. - 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? - Exam average

Average of marks that have on the certificates students of 8.A class in mathematics is exactly 2.45. If we did not add 1 and 3 of sutdents Michael and Alena, who arrived a month ago, it would average exactly 2.5. Determine how many students have class 8. - Arc

The length of the circle is 33 amd arc length of the circle 11. What is the magnitude of the angle of this arc? - Jan

Jan is 13 years and Peter 21 years old. For how many years will their ages in the ratio of 7:9? - Warehouse cars

From the warehouse started truck at speed 40km/h. After 1hour 30mins started from the same place same direction a car at speed 70 km/h. For how long and at what distance from the warehouse overtake a truck? - Chess

How many ways can select 3 fields on classic chess board with 64 fields, so that fields don't has the same color? - 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? - Diamond

Side length of diamond is 35 cm and the length of the diagonal is 56 cm. Calculate the height and length of the second diagonal. - Base

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

Diagonal of the rectangle has length 14 cm. Angle between diagonal and londer sife of rectangle is 37°. Calculate area of the rectangle. - Four-digit number

Find also a four-digit number, which quadrupled written backwards is the same number. - Cross-country competition

Cross-country competition was attended by 76% of pupils of class 9.B. Class consis of 16 boys, two of whom did not run and 4 girls did not run. How many girls go to class 9.B? - Katy MO

Kate draw triangle ABC. Middle of AB have mark as X and the center of the side AC as Y. On the side BC wants to find the point Z such that the content area of a 4gon AXZY was greatest. What part of the triangle ABC can maximally occupy 4-gon AXZY?

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