Math practice for 13 year olds - page 425 of 428

Number of problems found: 8555

Guests
How many ways can 8 guests sit down on 10 seats standing in a row?
Window
Peter knocked a 100 × 67 cm opening in the wall for a window frame. When the glazier installs the frame and glass, the glass will be 13.5 cm from the edge of the opening on each side. By what percentage less light enters through the glass than through the
VAT
VAT is a tax on which the state artificially betrays goods and services for final consumption. VAT in Slovakia is 20%. Calculate how much percent pay fewer tax residents of Japonska when VAT is only 5%.
Circumference - a simple
What is the ratio of the circumference of any circle to its diameter? Write the result as a real number rounded to 2 decimal places.
Tangents
From point R, two tangents are drawn to a circle with a radius of 41 cm. The distance between the two points of tangency is 16 cm. Calculate the distance from point R to the centre of the circle.
Discounts on rail (ZSSK)
The railway company ZSSK offers a discount of 40% (SENIOR RAILPLUS) for 9.9 Eur/year. Calculate the real discount rate as a percentage, where passengers will travel 5 Eur per week.
Solidarity
Calculate how many kilograms of salt a citizen effectively 'donates' to the government through taxes each year, if the combined tax burden (VAT + income tax + other levies) is 53% of a gross monthly salary of 982 euros and 1 kg of salt costs 15 cents.
Sphere A2V
The surface of the sphere is 241 mm². What is its volume?
Sphere fall
How much percent fall volume of a sphere if the diameter decreases 3×?
Sphere growth
How many times does a volume of the sphere rise if priemer rises 10×?
Density - simple example
Material of density of 1189 kg/m³ occupies a container volume of 64 cm³. What is its mass?
Floating barrel
A barrel (cylindrical in shape) floats on water with its top 18 dm above the water surface. The width of the part of the barrel above the waterline is 34 dm. The length of the barrel is 12 dm. Calculate the volume of the barrel.
3y inflation
The price of the cookie rise in the first year by 2%, the second year fell by 6%, and in the third year increased by 17%. Calculate the average annual increase in the price of the cookie.
Inflation
Once upon a time, a ruler had a printing press and printed money endlessly. As a result, prices rose by 2.7% in the first year, 2.1% in the second, 3.6% in the third, and 5.4% in the fourth. The ruler then lost an election. Calculate the average annual in
Circles
Three circles with radii 30 cm, 28 cm, and 37 cm are mutually tangent externally. What is the perimeter of the triangle whose vertices are the centres of the circles?
Insurance
The house owner is insured against natural disasters and pays 0.05% annually of the value of the house 88 Eur. Calculate the value of the house. Calculate the probability of disaster if you know that 50% of the insurance is to pay damages.
Two doctors
Doctor A makes the correct diagnosis with a probability of 89% and Doctor B with a probability of 75%. Calculate the probability of a correct diagnosis if both doctors examine the patient independently.
Present
A gift box has the shape of a cuboid with dimensions 8 × 8 × 3 cm. Miloslav wants to wrap it using square sheets of paper with sides of 18 cm. How much paper is left over?
Monkey
The monkey fell into 20 meters deep well. Every day it climbs 3 meters, at night it drops back by 2 m. On what day it gets out from the well?
Mine
The wheel in a mine hoist has a diameter of 4 m. How many metres does the elevator cabin travel if the wheel rotates 89 times in the same direction?

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