Examples for 8th grade - page 17

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?
Hexagonal pyramid
Calculate the volume and the surface of a regular hexagonal pyramid with a base edge length 3 cm and a height 5 cm.
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
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
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.
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.
EQL triangle
Calculate inradius and circumradius of equilateral triangle with side a=77 cm.
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.
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/m³
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.
Block
Calculate the volume of a cuboid ABCDEFGH if |AB| = 16 cm, |BC| = 19 cm and the angle ∠CDG = 36.9°
Cube wall
Surface of first cube wall his 225 mm². Second cube area is 60% of the surface of the first cube. Determine the length of the edge of the second cube (x).
Sphere A2V
Surface of the sphere is 296 cm^2. What is its volume?
Scrap
From 6 products are 3 scrap. What is the probability that the random pick of 2 products have no defective product?
Steamship
Between the two ports on the river is going steamship. The journey there and back takes 8:42. Downstream steamship traveling at 20 km/h, upstream 9 km/h. What is the distance between the ports?
Triangle angles
The angles α, β, γ in triangle ABC are in the ratio 6:2:6. Calculate size of angles.
Three workers
Three workers A, B, C have to work on a specific task. Workers A and B completed whole task in 11 days, B together with C for 15 days, A together with C for 24 days. How long it would take to complete the task every one of them alone? How long it would.
Leveling
Calculate how many 25 kg bags of leveling concrete must be purchased if we leveling room 15 m² to the "height" 6 mm if consumtion is 1.5 kg per square meter and millimeter thickness.

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