# Examples for 8th grade - page 38

- 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? - Supplementary angles

One of the supplementary angles are three times larger than the other. What size is larger of supplementary angles? - Little hand

What angle shifted little hand on the clock after one hour and 38 minutes? - Logs

The log has diameter 30 cm. What's largest beam with a rectangular cross-section can carve from it? - Pool 2

The first supply by the pool fill for five hours and the second fill for six hours, drain should be drained for 15 hours. For how many hours the pool is full, when we open both inlet now and outlet open two hours later? - RT 11

Calculate the area of right tirangle if its perimeter is p = 46 m and one cathethus is 18 m long. - CD disc

A compact disc has a diameter of 11.8 cm. What is the surface area of the disc in square centimeters? - Diameter

If the endpoints of a diameter of a circle are A(10, -5) and B (8, 7), what is the radius of the circle? - Carpenter

From wooden block carpenter cut off a small cuboid block with half the edge length. How many percent of wood he cut off? - Racer

The first racer run at a speed 12 m/s and is 470 meters before the finish and ahead 22 meters before second competitor. At what speed must run the second racer to catch first racer at the finish line? - Two valves

Water fill the pool by two valves for 16 days. After 6 days the first valve was stopped and the second valve fill pool for 12 days. How many days took to fill the pool each of the valves individually? - Plastic pipe

Calculate weight of the plastic pipe with diameter d = 60 mm and length 400 cm if the wall thickness is 6 mm and the density of plastic is 1228 kg/m^{3.} - Task

I have homework. The cube has an edge 11 cm long and I must find wall and body diagonal. - Rhombus and inscribed

Rhombus has side a = 72 cm, the radius of the inscribed circle is r = 10 cm. Calculate the length of its two diagonals. - Angles

Determine the interior angles of a rhombus with area 240.6 cm^{2}and perimeter 64 cm. - Acids

76% acid was make from same acid of two different concentrations. Amount weaker acid to the stronger acid is in ratio 2:1. What was the concentration of the weaker acid, if stronger had 94% concentration? - Motion

From two different locations distant 104 km started against car and bus. The car started at 5:30 with average speed 58 km/h. Bus started at 6:40 with average speed 79 km/h. When they meet? How many kilometers went the bus? - Rotation

Right triangle with legs 9 cm and 16 cm rotate around longer leg. Calculate the volume and surface area of the formed cone. - Numbers

Determine the number of all positive integers less than 2937474 if each is divisible by 11, 23, 17. What is its sum? - Tinsmith

Tinsmith construct chimney pipe 126 cm long and 11 cm wide. What are the dimensions of the sheet will have to prepare for the construction of a pipe when the plate overlap at the joint add $x cm width of the plate?

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