# Examples for 8th grade - page 12

- Hole

In the center of the cube with edge 14 cm we will drill cylinder shape hole. Volume of the hole must be 27% of the cube. What drill diameter should be chosen? - Air

Room is 40.1 m long, 25.2 dm wide and 369 cm high. How many people can simultaneously be in this room if for hygiene reasons is calculated 5100 dm^{3}of air per person? - Parquet floor

Three workers laid parquet floor for 2.9 hour. The first one would do this work alone 9 hours, the second in 7 hours. For how many hours would fulfill this work the third worker, if he worked alone? - Tinsmith

Tinsmith construct chimney pipe 145 cm long and 15 cm wide. What are the dimensions of the sheet will have to prepare for the construction of a pipe when the plate overlap at the joint add $x cm width of the plate? - Radius

Determine the radius of the circle, if its perimeter and area is the same number. - Cu wire

Copper wire has a length l = 980 m and diameter d = 8 mm. Calculate the weight if density of copper is ρ = 8500 kg/m^{3}. Result round to one decimal place. - Discount

Product has been discounted twice by 19%. What is the total discount given? - Pool

Mr. Peter build a pool shape of a four-sided prism with rhombus base in the garden. Base edge length is 8 m, distance of the opposite walls of the pool is 7 m. Estimated depth is 144 cm. How many hectoliters of water consume Mr. Peter to fill the pool? - Seedcake

Seedcake costs 44 cents. How many minimum seedcakes we must buy that we can pay in cash only whole euros? - Madams

During the spring cleaning ladies going to wash windows. Mother takes wash all the windows 5 hours, the grandmother 3 times longer and Paula wash all windows in 2 hours. How many hours will spend washing the windows this "women's team" if working togethe - Diofant equation

In the set of integers (Z) solve the equation: ? Write result with integer parameter ? (parameter t = ...-2,-1,0,1,2,3... if equation has infinitely many solutions) - Cuboid

Determine the dimensions of cuboid a, b, c; if diagonal d=9 dm has angle with edge a α=55° and has angle with edge b β=58° - Octahedron - sum

On each wall of a regular octahedron is written one of the numbers 1, 2, 3, 4, 5, 6, 7 and 8, wherein on different sides are different numbers. For each wall John make the sum of the numbers written of three adjacent walls. Thus got eight sums, which also. - Phone numbers

How many 9-digit telephone numbers can be compiled from the digits 0,1,2,..,8,9 that no digit is repeated? - Cubes

Cube, which consists of 27 small cubes with edge 4 dm has volume: - Freedom

In the city are 3/9 of women married for 3/6 men. What proportion of the townspeople is free (not married)? Express as a decimal number. - Clocks

How long path will walk the end of the clock's minute-hand long 7 cm for 330 minutes? How long will walk in the same time hour-hand? - Square diagonal

Calculate the length of diagonal of the square with side a = 23 cm. - Vinegar

We must dilute 16 liters of 8.8% aqueous vinegar to 4.1% one. How much water is necessary to add? - Building

How high is the building that throws horizontal shadow 95.4 m long at angle 50°?

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