# Examples for 8th grade - page 72

- Grass seeds

How many kg of grass seed is needed to be sowing a circular field with a diameter of 120 meters when the 1 m^{2}should be used 0.8 grams seeds? - Concrete box

The concrete box with walls thick 7 cm has the following external dimensions: length 1.7 m, width 31 cm and height 45 cm. How many liters of soil can fit if I fill it to the brim? - Motion 2

At 10 o'clock started from place A car speed at 90 km/h. 20 minutes after started from the place B at speed 60 km/h another car. Distance places A and B is 120 kilometers. What time and where they meet? - Chord 4

I need to calculate the circumference of a circle, I know the chord length c=19 cm and the distance from the center d=33 cm chord to the circle. - Star

Calculate the content of the shaded part of square with side 43 cm. - Annulus

Two concentric circles form an annulus of width 10 cm. The radius of the smaller circle is 20 cm. Calculate the content area of annulus. - Blackjack TU160

Bomber Tupolev TU160 started at 9:00 from the airport and flew at average speed of 1850 km/h toward the airfield B distant 3500 km. After evaluating the danger from the airport B started at 9:45 B towards A fighter MIG 29 at an average speed 2300 km/h. At - Giant coin

From coinage metal was produced giant coin and was applied so much metal, such as production of 10 million actual coins. What has this giant coin diameter and thickness, if the ratio of diameter to thickness is the same as a real coin, which has a diameter - 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 ? - High wall

I have a wall 2m high. I need a 15 degree angle (upward) to second wall 4 meters away. How high must the second wall? - Tin with oil

Tin with oil has the shape of a rotating cylinder whose height is equal to the diameter of its base. Canned surface is 1884 cm^{2.}Calculate how many liters of oil is in the tin. - Juice box 2

Box with juice has the shape of a cuboid. Internal dimensions are 15 cm, 20 cm and 32 cm. If the box stay at the smallest base juice level reaches 4 cm below the upper base. How much internal volume of the box fills juice? How many cm below the top of the - Angles of the triangle

ABC is a triangle. The size of the angles alpha, beta are in a ratio 4: 7. The angle gamma is greater than the angle alpha by a quarter of a straight angle. Determine angles of the triangle ABC. - Concentric circles

In the circle with diameter 17 cm is constructed chord 12 cm long. Calculate the radius of a concentric circle that touches this chord. - Three men

Alex is half younger than Jan, which is one-third younger than George. The sum of their ages is 48. How are these three men old? - RT and ratio

Right triangle whose cathetus are in a ratio 6:17 has hypotenuse 47 m long. How long are cathetus? - Football season

Throughout the football season gave Adam the 23 goals more than Brano and 16 goals less than Karol. Edo gave the 6 goals more Dušan. Karol gave 5 more than Edo. Brano and Edo gave together 17 goals. How many goals gave each boy and how many goals gave the. - Workers

Workers digging a jump pit in the school yard. Pit has a cuboid shape with a length 20 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? - Wheel

Diameter of motocycle wheel is 63 cm. How many times rotates wheel on roand long 1 km? - Sphere - parts

Calculate the area of a spherical cap, which is part of an area with base radius ρ = 15 cm and a height v = 2.5 cm.

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