Examples for 8th grade - page 73
- The factory
The factory ordered 500 hexagonal steel bars of square section with 25 mm side. How many cars with a load capacity of 3 tonnes will be needed for bars move if the steel density is 7,850 kg.m-3?
- Eight palm
There grows 8 palms by the sea. At the first sitting one parrot, on second two, on third sits four parrots on each other twice the previous parrots sitting on a previous palm. How many parrots sitting on eighth palm?
- Cuboid - edges
The cuboid has dimensions in ratio 4: 3: 5, the shortest edge is 12 cm long. Find: (A) the lengths of the remaining edges, (B) the surface of the cuboid, (C) the volume of the cuboid
- Three figures - numbers
The sum of three numbers, if each is 10% larger than the previous one, is 662. Determine the figures.
- Right triangle eq2
Hypotenuse of a right triangle is 9 cm longer than one leg and 8 cm longer than the second leg. Determine the circumference and area of a triangle.
- Gasoline tank cylindrical
What is the inner diameter of the tank, which is 8 m long and contains 40 cubic cubic meters of gasoline?
Theatrical performance was attended by 480 spectators. Women were in the audience 40 more than men and children 60 less than half of adult spectators. How many men, women and children attended a theater performance?
- Mr and Mrs
Mr. Calda and Mrs. Cald have a total of 139 years. How many years have when we know that Mr. Calda is 9 years older than Mrs. Cald
Two trams started at the same time from the same place. One tram journey takes 30 minutes and the second 45 minutes to its final stop. How long will trams meet again?
The driver of the supply car reckoned that at the average speed of 72 km/h arrives to the warehouse for 1 1/4 hours. After 30 km however unintentionally drove to the gas station and have ten minutes delay. At what average speed would have to go the rest.
Mom is 39 years old. Karl is eight years and Paul 4 years. For many years mother would old just like two children together?
- Image scale
The actual image dimensions are 60 cm x 80cm and has a reduced size 3 cm x 4 cm. At what scale the image was reduced?
Denis and Zdeno together have 97 coins. If Denis had 4 coins less than he has now, the number of the coins would be in the ratio 14: 17. Determine the number of coins owned by Denis and Zdeno.
Assistant rewrote 15% of the entire manuscript in 12 hours. How many hours must still write to rewrite the rest of the manuscript?
- Family parcels
In father will he divided the land so that the older son had three bigger part than younger son. Later elder son gave 2.5 ha field to younger and they had both the same. Determine the area of family parcel.
Cableway has a length of 1800 m. The horizontal distance between the upper and lower cable car station is 1600 m. Calculate how much meters altitude is higher upper station than the base station.
- Class 9A
On the final certificate have one quarter of the class 9A mark "C" of mathematics, seventh mark "C" from the Czech language and two students failed in chemistry. How many students attend class 9A?
- Hydrochloric acid
Determine the concentration of which must have a solution of hydrochloric acid that mixing 10 l of the solution with 8 liters of 26% solution to get the solution with a concentration of 50%?
- Base, percents, value
Base is 344084 which is 100 %. How many percent is 384177?
- Right triangle ABC
Calculate the perimeter and area of a right triangle ABC, if you know the length of legs 4 cm 5.5 cm and 6.8 cm is hypotenuse.