# Examples for 8th grade - page 17

- Wire D

Wire length 1 m is bent so that it forms a semicircle circuit (including the diameter). Determine the radius of the semicircle. - Rotating cone II

Calculate area of surface of rotating cone with base radius r=19 cm and height h=9 cm. - Triangle in circle

Vertices of the triangle ABC lies on a circle with radius 3 so that it is divided into three parts in the ratio 4:4:4. Calculate the circumference of the triangle ABC. - Cyclists

Cyclist who rides at an average speed 16 km/h travels trip distance 10 min before the cyclist who rides at an average speed 11 km/h. What is the length of this cyclist trip(distance in km)? - Arm

Calculate the length of the arm r of isosceles triangle ABC, with base |AB| = 18 cm and a height v=17 cm. - Scouts

The boys from scout group traveled 5 days distance 115 km. Every day walked 1.5 km less than the previous day. How many kilometers scouts walked in the first day? - Magnification of the square

If we increase the square side, increase the content of the 80 %. About what percentage was increased his sides? - Two balls

Two balls, one 8cm in radius and the other 6cm in radius, are placed in a cylindrical plastic container 10cm in radius. Find the volume of water necessary to cover them. - Cardboard box

We want to make a cardboard box shaped quadrangular prism with rhombic base. Rhombus has a side of 5 cm and 8 cm one diagonal long. The height of the box to be 12 cm. The box will be open at the top. How many square centimeters cardboard we need, if we cal - Scrap

From 6 products are 3 scrap. What is the probability that the random pick of 2 products have no defective product? - Hollow sphere

Steel hollow sphere floats on the water plunged into half its volume. Determine the outer radius of the sphere and wall thickness, if you know that the weight of the sphere is 0.5 kg and density of steel is 7850 kg/m^{3} - Tanker

An oil tanker can be emptied by the first pump in 4.9 hours. Second pump can empty an tanker in 8 hours. If the first pump started at 4:00 and second 1.4 hour later, at what time will the tanker be empty? - Election mathematics

In elections, 14 political parties received this shares of voters: party A 49.8 %party B 11.4 %party C 7.9 %party D 6.3 %party E 6.1 %party F 5.7 %party G 4.6 %party H 2.9 %party I 2.2 %party J 1.3 %party K 1 %party L 0.7 %party M 0.1 % Calculate what th - Cone and the ratio

Rotational cone has a height 23 cm and the ratio of the base surface to lateral surface is 7: 9. Calculate a surface of the base and the lateral surface. - EQL triangle

Calculate inradius and circumradius of equilateral triangle with side a=77 cm. - Water inlets

Inlet valve with a flow rate of 12 liters per second is filled tank for 72 minutes. How long take to fill full tank if we open one more such valve half an hour after? - Sector

The perimeter of a circular sector with an angle 1.8 rad is 64 cm. Determine the radius of the circle from which the sector comes. - Sphere A2V

Surface of the sphere is 241 mm^{2}. What is its volume? - Truck

Truck went for 4 hours and 48 minutes. If truck increase speed by 21 km/h, went same distance in 1.8 hours. Calculate this distance. - Cube wall

Surface of first cube wall his 225 mm^{2}. Second cube area is 60% of the surface of the first cube. Determine the length of the edge of the second cube (x).

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