Maths practice for 12-year-olds - page 352 of 355

Number of problems found: 7083

Flags
How many different flags can be made from green, white, blue, red, orange, yellow, and purple materials, so each flag consists of three different colors?
Carbon dioxide
Calculate how many grams of oxygen are in 59 grams of carbon dioxide CO₂. The relative atomic mass of oxygen is 16, and of carbon is 12.
Iron
Iron ore contains 61% iron. How much iron ore is needed to produce 29 tons of iron?
Air mass
What is the weight of the air in a classroom with dimensions 10 m × 3 m × 3 m? The air density is 1.293 kg/m³.
Barrel of oil
The barrel of oil weighs 283 kg. When it molded 26% oil, it weighed 216 kg. What is the mass of the empty barrel?
Copper plate
Copperplate length 9 m and width 56 cm weigh 48.38 kg. What is the plate thickness if 1 m³ of copper weighs about 8700 kg?
Magnification of the square
If we increase the square side, increase the area of the 57 %. About what percentage was increased on its side?
Circle and angle
What is the length of the arc of a circle with radius r = 432 dm with central angle 0.53 rad?
Promile
Calculate the 17.6 ‰ of 353.
Slovakia banks
It is an unwritten rule that the larger bank in Slovakia (number of clients, balance sheet) has the worst / more expensive services offered to clients. Perhaps customs and herd customers prefer only the trio SLSP, VUB, and Tatrabanka. Calculate how many t
Tesco Clubcard
František got quarterly billing vouchers for Tesco ClubCard, taking goods worth 6.5 Eur. Calculate the average monthly amount Tesco stores bought goods. Tesco ClubCard works for every Euro spent; you get one ClubCard point, which Tesco will convert to one
Human buying irrationality
I longer watch processors for Socket A on the secondhand market, Athlon XP 1.86GHz with a PR rating of 2500+ costs $7, and Athlon XP 2.16Ghz with a PR rating of 3000+ currently costs $16. Calculate: About what percentage of the Athlon XP 2.16Ghz is more p
Quiz
The tested student answered correctly on a 3/6 question. The wrong answer was 16. How many questions were answered?
Barrel with liquid
Barrel with obilím weight 123 kg. When it sheds 56% of obilia, ha weight 74 kg, what is the weight of an empty barrel?
Trapezium zoom
How many times should the area of the trapezoid be increased if all sides and altitudes increase 5 times?
Sumo competition
In the competition for the heaviest man was 5 competitors. The first three together weighed 369 kg. What is the minimal weight of the winner if a contestant weighed with an accuracy of one kilogram?
Triangle angles
The angles α, β, γ in triangle ABC are in the ratio 6:2:6. Calculate the size of angles.
Degrees to radians
Convert magnitude of the angle α = 538°38'17" to radians:
Rectangle A2dim
Calculate the side of the rectangle if you know that its area is 950 m² and one side is 38 m.
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%.

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