# Examples for 9th grade - page 68

- Octahedron

All walls of regular octahedron are identical equilateral triangles. ABCDEF octahedron edges have a length d = 6 cm. Calculate the surface area and volume of this octahedron. - Prism - eq triangle

Calculate the volume and surface of the prism with the base of an equilateral triangle with side a = 4cm and the body height is 6cm. - Midnight

How many hours are, if the time that elapsed since 8:00 is 2/5 of the time that will past till midnight? - Grass

Peter and Stano lawn grass for 3 hours 12 minutes. How long would it take to Peter if Stano lawn grass himself for 384 minutes. - Principal and interest

Peter put € 270 principal into bank and at the end of the year on account was € 282. To what annual interest rate that Peter had deposited money in the bank? - Billboard

Rectangular billboard is 2.5 m long with a diagonal 2.8 m long. Calculate the perimeter and the content area of the billboard. - Barrel 4

Barrel of water weighs 63 kg. After off 75% water, the weight of the barrel with water is 21 kg. How many kg weigh empty barrel and how many kgs water in it? - Mass

The thickness of a metallic tube is 1cm and its outer radius is 11cm. Find the mass of such 1m long tube, if the density of the metal is 7.5g per cubic cm. - Water channel

The cross section of the water channel is a trapezoid. The width of the bottom is 19.7 m, the water surface width is 28.5 m, the side walls have a slope of 67°30' and 61°15'. Calculate how much water flows through the channel in 5 minutes if the water flow - Largest angle of the triangle

What is the largest angle of the triangle if the second angle is 10° greater than twice the first and the third is 30° smaller than the second? - Collecting

For the first week of material collection events are picked up at the school 850 kg of paper and 305 kg of rags which represented 55% of total collection for 14 days. How many kilograms of secondary raw materials were handed over totally? - Apples 2

How many apples were originally on the tree, if the first day fell one third, the second day quarter of the rest and on tree remained 45 apples? - Cuboid and ratio

Cuboid has dimensions in ratio 1:2:6 and the surface area of the cuboid is 1000 dm^{2.}Calculate the volume of the cuboid. - Skiing meeting

On the skiing meeting came four friends from 4 world directions and led the next interview. Charles: "I did not come from the north or from the south." Mojmir "But I came from the south." Joseph: "I came from the north." Zdeno: "I come from the south." W - Numbers

Write smallest three-digit number, which in division 5 and 7 gives the rest 2. - Savings and retirement

The older sibling has saved 44% more euros than the youngest, which represents 22 euros. How many euros older brother has saved ? - Password dalibor

Kamila wants to change the password daliborZ by a) two consonants exchanged between themselves, b) changes one little vowel to such same great vowel c) makes this two changes. How many opportunities have a choice? - Bath salts

Bath salt A weighs 900 grams and costs 36,40 CZK. Bath Salts B weighs 1000 grams, but costs 85 CZK. How much is a bath salt A cheaper than B one? - Hollow sphere

The volume of the hollow ball is 3432 cm^{3.}What is its internal radius when the wall thickness is 3 cm? - Buttons

Shirt has 6 buttons, blouse has 4 buttons. All buttons are 176. Shirts and blouses are together 36. How many are the shirts and blouses?

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