# The most difficult problems

#### Number of problems found: 7486

- Angle of two lines

There is a regular quadrangular pyramid ABCDV; | AB | = 4 cm; height v = 6 cm. Determine the angles of lines AD and BV. - Equilateral triangle vs circle

Find the area of an equilateral triangle inscribed in a circle of radius r = 9 cm. What percentage of the circle area does it occupy? - A photograph

A photograph will stick to a white square letter with a x cm length. The photo is 3/4 x cm long and 20 cm wide than the width of the paper. The surface of the remaining paper surrounding the photograph is 990 cm^{2}. Find the size of paper and photo. - Castle model

The castle model has a cone-shaped roof. The cone side is 45 cm long and the base radius is 27 cm. a) What is the roof volume? b) How many dm^{2}of wallpaper is used to glue the roof, ie the cone shell? c) What is the weight of the roof if it is made of woo - The difference

The difference of two numbers is 1375. If their exact quotient is 12. Find the two numbers - Three gardens

Is it possible to divide a plot of land with an area of 920 m^{2}into three gardens in a ratio of 4: 2: 3 so that their areas are only whole multiples of square meters? - Profit growth

The profit of a company increased by 25% during the year 1992, increased by 40% during the year 1993, decreased by 20% in 1994 and increased by 10% during the year 1995. Find the average growth in the profit level over the four years periods? - Pile of sand

A large pile of sand has been dumped into a conical pile in a warehouse. The slant height of the pile is 20 feet. The diameter of the base of the sandpile is 31 feet. Find the volume of the pile of sand. - A screen

A screen is 1680 x 1050 pixels. What are the coordinates (and size in pixels) of an centered area which is exactly 33% of the screen size? - Mixing Celsius and Fahrenheit

Add up three temperatures: 5°F +6°F +0°C - Hyperbola equation

Find the hyperbola equation with the center of S [0; 0], passing through the points: A [5; 3] B [8; -10] - Coordinates of square vertices

The ABCD square has the center S [−3, −2] and the vertex A [1, −3]. Find the coordinates of the other vertices of the square. - Closed drum

Find the total surface area of a closed cylindrical drum if it's diameter is 50 cm and height is 45 cm. (π= 3.14) - KLM triangle

Find the length of the sides of the triangle KLM if m = 5cm height to m = 4.5 cm and size MKL angle is 70 degrees. - Find the sum

Find the sum of all natural numbers from 1 and 100, which are divisible by 2 or 5 - The size

The size of a Trapezium are 3/4×cm, ×cm 2(×+1)cm and 3(×+2)cm long respectively if it's perimeter is 60cm, calculate the length of each side. - Sum of dividend

Suppose X is divided separately 2.63 and 1.40. And the results of the individual divisions are added to give a result less than X. What is X? - Unknown mixed number

Find the number that is smaller than 5 5/12 by as much as 2 2/13 is smaller than 6 1/6 - Calculate 3

Calculate the cube volume whose edge is 3x-1,3x-1,3x-1 - Simplify

Simplify expression - which expression is equivalent to: 3(m + 2) − 4(2m − 9)

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