# Examples for 8th grade - page 78

- Cuboid - ratios

The sizes of the edges of the cuboid are in the ratio 2: 3: 5. The smallest wall have area 54 cm^{2.}Calculate the surface area and volume of this cuboid. - Isosceles trapezoid

Calculate the circumference and the contents of the isosceles trapezoid if you know the size of the bases is 8 and 12 cm and the size of the arms is 5 cm. - Lawns

Before a sports hall are two equally large rectangular lawns, each measuring 40 m and 12 m. Maintenance of 10m² lawn cost 45 CZK yearly. On each lawn is circular flowerbed with a diameter 8 meters. How much money is needed each year to take on lawn care?. - Sales off 2

Computer monitor sold for 8400 CZK in March. In April, dealer price decreased by 798 CZK. Calculate the percentage by which the price was reduced. - Sugar 9

150 kg of sugar beet yields 24 kg of sugar. From how many tons of sugar beet can be obtained three tons of sugar? - Combinations of sweaters

I have 4 sweaters two are white, 1 red and 1 green. How many ways can this done? - Divisible by 5

How many three-digit odd numbers divisible by 5, which are in place ten's number 3? - Chord circle

The circle to the (S, r = 8 cm) are different points A, B connected segment /AB/ = 12 cm. AB mark the middle of S'. Calculate |SS'|. Make the sketch. - Contestants

In the competition it was possible to get 0-5 points. In fact, 5 contestants of the 15 best contestants has earned 5 points or 4 points (which have won 10 contestants). The number of contestants who earned 3 points was the same as the number of contestan - Equation

? - Painting a hut

It is necessary to paint the exterior walls of hut whose layout is a rectangle of 6.16 m x 8.78 m wall height is 2.85 meters. Cottage has five rectangular windows; three have dimensions of 1.15 m x 1.32 m and two 0,45 m x 0.96 m. How many m^{2}is necessary - Three-digit

How many three-digit natural numbers do not have the number 7? - Scale 3

Miriam room is 3.2 meters wide. It is draw by line segment length 6.4 cm on floor plan. In what scale it is plan of the room? - Pyramid Z8–I–6

Each brick of pyramid contains one number. Whenever possible, the number in each brick is lowest common multiple of two numbers of bricks lying directly above it. That number may be in the lowest brick? Determine all possibilities. - Earth and Sun

Earth is 150 million km away from the Sun, 300,000 km of sunlight travels in 1 second. How long will the light come from the Sun to the Earth? - Cars 6

At 9:00 am two cars started from the same town and traveled at a rate of 35 miles per hour and the other car traveled at a rate of 40 miles per hour. After how many hours will the cars be 30 miles apart? - Working together

One painter paint the nursery in 10 days, the second in 8 days. How many days will the nursery be painted if they work together? - Angles in ratio

The size of the angles of the triangle are in ratio x: y = 7: 5 and the angle z is 42° lower than the angle y. Find size of the angles x, y, z. - Church roof 2

The roof has the shape of a rotating cone shell with a base diameter of 6 m and a height of 2.5 m. How many monez (CZK) will cost the roof cover sheet if 1 m^{2}of metal sheet costs 152 CZK and if you need 15% extra for joints, overlays and waste? - Hypotenuse

Calculate the length of the hypotenuse of a right triangle with a cathetuses 71 cm and 49 cm long.

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