# Examples for 8th grade - page 67

- Cube diagonals

Determine the volume and surface area of the cube if you know the length of the body diagonal u = 216 cm. - After 16 years

After 16 years will Dana be five times older as she was four years ago. After how many years will Dana celebrate her 16th birthday? - Sides od triangle

Sides of the triangle ABC has length 4 cm, 5 cm and 7 cm. Construct triangle A'B'C' that are similar to triangle ABC which has a circumference of 12 cm. - Truncated cone

A truncated cone has a base radius 40 cm and 10 cm and a height of 25 cm. Calculate its surface area and volume. - Interst on savings

The bank offers 1.6% interest. How many euros have to insert at the beginning if we received € 15 on the interest? - Cube

Calculate the surface of the cube ABCDA'B'C'D' if the area of rectangle ACC'A' = 344 mm^{2.} - Book

Alena read a book at speed 15 pages per day. If she read twice as fast she should read a book four days earlier. How many pages have a book? - Heating plant

Workers dump imported coke at heating plant. On the first day used half of the amount, the second day three quarters the rest and on the third day left 120 tons. How much coke they dump at heating plant? - Drainage channel

The cross section of the drainage channel is an isosceles trapezoid whose bases have a length of 1.80 m, 0.90 m and arm has length 0.60 meters. Calculate the depth of the channel. - Meat

Half a kilogram of pork and three-quarters of a kilogram of beef cost total 5.1 USD. One quarter of a kilogram of beef and 1 kilogram of pork cost 4.9 USD. Determine the price of 1 kg of each type of meat. - Shoes and slippers

Shoes were three times as many as slippers. If shoes were cheaper by 120, it would be twice as expensive as slippers. How much cost shoes and how much slippers? - Railway wagon

The railway wagon holds 75 m^{3}load. Wagon can carry a maximum weight of 30 tonnes. What is the maximum density that may have material with which we could fill this whole wagon? b) what amount of peat (density 350 kg/m3) can carry 15 wagons? - Percentage and rectangle

About what percentage increases perimeter and area of a rectangle if both the sides 12 cm and 10 cm long we increase by 20%? - Chord distance

The circle k (S, 6 cm), calculate the chord distance from the center circle S when the length of the chord is t = 10 cm. - Isosceles - isosceles

It is given a triangle ABC with sides /AB/ = 3 cm /BC/ = 10 cm, and the angle ABC = 120°. Draw all points X such that true that BCX triangle is an isosceles and triangle ABX is isosceles with the base AB. - Rain

How many mm of water rained the roof space 75 m^{2}if the empty barrel with a radius of 8 dm and height 1.2 m filled to 75% its capacity? :-) - Trapezoid v3

The isosceles trapezoid has the angle at a firsst base 40 degrees less than the angle at second base. How large angles has this trapezoid ? - Sweets

3 chocolate and 7 cakes cost 85, - CZK. 2 chocolates and 6 cakes cost 86, - CZK. How much is 5 chocolates and 9 cakes? I wonder how to get the result, but only by logic without the use of a system of equations - Diamond

Calculate the length of the two diagonals of the diamond if: a = 13 cm v = 12 cm - New computer

New computer process a certain amount of data for 6 hours. For how many hours will process the same amount of data older computer that has a quarter lower performance?

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