# Examples for 8th grade - page 57

- Family and age ratios

Age of father and son are in the ratio 10:3; age of father and daughter are in the ratio 5:2. How old is father and son, if daughter is 20 years old? In what ratio is age sister and brother? - EQL triangle

Calculate inradius and circumradius of equilateral triangle with side a=100 cm. - Trapezoid ABCD

Calculate the perimeter of trapezoid ABCD if we know the side c=25, b=16 which is also a height and side d=27. - Against each other

From two points A, B distant 45 km at the same time started two cars against each other at speeds 81 km/h and 67 km/h. How long does cars meet and what distance passes each of them? - Tower

How many m^{2}of copper plate should be to replace roof of the tower conical shape with diameter 13 m and the angle at the vertex of the axial section is 150°? - Lid

What is the weight of concrete cover (lid) to round shape well with a diameter 1.3 m, if the thickness of the cover is 15 cm? 1 m^{3}of concrete weighs 2190 kg. - Block

Calculate the volume of a cuboid ABCDEFGH if |AB| = 11 cm, |BC| = 8 cm and the angle ∠CDG = 29.4° - Hop-garden

The length of the rectangular hop garden Mr. Smith increased by 20% and its width by 20%. What is the percentage change in area of hop garden? - Negative percentage

In 2003, the company had a loss of 25600 Euros. Two years later he was already in profit 25200 Eur. Calculate what percentage of the company increased profits in this two years. - Wire D

Wire length 5 m is bent so that it forms a semicircle circuit (including the diameter). Determine the radius of the semicircle. - Right isosceles

Calculate area of the isosceles right triangle which perimeter is 35 cm. - Wheat

The rectangle shaped field with dimensions 979 m and 540 m harvested last year was 2775 q wheat. (1 q = 1 quintal = 100 kg). During the year, it was necessary to fix the pipe and therefore did kick wide 6 m parallel to the side of the field 540 m, where no - Triangle

Calculate heights of the triangle ABC if sides of the triangle are a=48, b=81 and c=98. - Window

Peter demolish box hole in the wall for window frame 48×48 cm. When they came masters fitted frame and window will be found that glass is 13.7 cm from the hole in each direction. Calculate how much percent less light enters the window than hole? - Clocks

How long path will walk the end of the clock's minute-hand long 24 cm for 110 minutes? How long will walk in the same time hour-hand? - Cu thief

The thief stole 121 meters copper wire with cross-section area of 101 mm^{2.}Calculate how much money gets in the scrap redemption, if redeemed copper for 5.5 eur/kg? The density of copper is 8.96 t/m^{3}. - Engineer Kažimír

The difference between politicians-demagogues and reasonable person with at least primary education beautifully illustrated by the TV show example. "Engineer" Kažimír says that during their tenure there was a large decline in the price of natural gas, pri - Isosceles right triangle

Contents of an isosceles right triangle is 18 dm^{2.}Calculate the length of its base. - Diagonals

Draw a square ABCD whose diagonals have a length of 6 cm - Doubling

The message is spreading that each day has doubled the number of people who know about it. All know message for 20 days. How long known it eighth people?

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