# Examples for 8th grade - page 20

- Dices

We will throw two dice. What is the probability that the ratio between numbers on first and second dice will be 1:2? - Train from Prague

First train from Prague started at 8:00 hour at 40 kilometers per hour. Train from Ostrava started at 9:20 at 80 km per hour. In how many hours and how far from cities with trains meet if the distance of cities is 400 km. - Water tank

Water tank shape cuboid has a width of 3.1 m and length twice larger. How high will reach water if water flow into 13 liters of water per second during 16 minutes? - Two workers

The first worker completed the task by himself in 9 hours, the second in 15 hours. After two hours of joint work left first worker to a doctor and the second finished the job himself. How many hours worked second worker himself? - The bridge

Across the circle lakepasses through its center bridge over the lake. At three different locations on the lake shore are three fishermen A, B, C. Which of fishermen see the bridge under the largest angle? - Triangle KLB

It is given equilateral triangle ABC. From point L which is the midpoint of the side BC of the triangle it is drwn perpendicular to the side AB. Intersection of perpendicular and the side AB is point K. How many % of the area of the triangle ABC is area o - Event probability

The probability of event P in 8 independent experiments is 0.33. What is the probability that the event P occurs in one experiment (probability is same)? - Box

Calculate the angle between box base 9 x 14 and body diagonal length 18. - Balance

The rod are 1.9 m long hanging weights 4 kg and 1 kg on ends. Where are centre of rod (distance from weight 4 kg) to be in balance? - Workers

Workers digging a jump pit in the school yard. Pit has a cuboid shape with a length 12 m, a width 20 dm and depth 36 cm. They excavate 0.4 cubic meters of soil an hour. How much time (hours and minutes) is need to the excavate this pit? - Glass mosaic

How many dm^{2}glass is nessesary to produc 39 slides of a regular 6-gon, whose side has length 23 cm? Assume that cutting glass waste is 12%. - Do you solve this?

Determine area S of rectangle and length of its sides if its perimeter is 102 cm. - Tank

In the middle of a cylindrical tank with a bottom diameter 251 cm is standing rod which is 13 cm above the water surface. If we bank rod its end reach surface of the water just by the tank wall. How deep is the tank? - Circumscribing

Determine the radius of the circumscribed circle to the right triangle with legs 9 cm and 6 cm. - Inscribed rectangle

The circle area is 216. Determine the area of inscribed rectangle with one side 5 long. - Map

Forest has an area of 36 ha. How much area is occupied by forest on the map at scale 1:500? - Root

Use law of square roots roots: ? - Shots

5500 lead shots with diameter 4 mm is decanted into a ball. What is it diameter? - Sales vs profit

Apple sells 22 percent less computes than the Acer but the profit from their sales is 2.2 times higher than Acer. How many times are Apple computer more expensive than Acer? - Triangular prism

Base of perpendicular triangular prism is a right triangle with leg length 5 cm. Content area of the largest side wall of its surface is 130 cm² and the height of the body is 10 cm. Calculate its volume.

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