Math practice for 13 year olds - page 204 of 431
Number of problems found: 8620
- Cone-shaped 23331
For his birthday, Jirka made a cone-shaped hat out of paper. The side of this cone is 35cm long, and the radius of its base is 20cm. How much dm of paper did Jirka use to make it? Thank you - Cone base
Calculate the circumference of the cone base; round the result to millimeters. If you know: radius 24 mm and height 46 mm. - Measuring 23281
We have a box with dimensions of 20cm, 16cm, and 8cm. How many cubes can fit in it if the cube has a size of 4cm? - The angles
The angles in the triangle are in the ratio 12:15:9. Find the angles. - The farmer
The farmer calculated that the supply of fodder for his 20 cows was enough for 60 days. He decided to sell two cows and a third of the feed. How long will feed the rest of the peasant's herd last? - Calculated 23231
There are 80 screws in the box with a total weight of 1.24 kg. The weight of one screw weighs 400g. Screw weight calculated in grams - Defective 23221
The factory sets a standard that 2% of products may be defective. Last week, out of 1,250 products, 32 were defective. How many defective products were the standard exceeded?
- Together 23211
Lenka is three times younger than her brother Lukas; they are 20 years old. How old is Lenka, and how many are Lukas? - Brother 23201
Karel would rake the leaves in the garden alone in 24 minutes. His younger brother would take 30 minutes. How long would they dig a garden if Karel digs alone for 6 minutes and his brother comes to his aid? - The manufacturer
The manufacturer found that 3% of the plates produced had a malfunction. Of the complaint, 75% are first and 25% second. What is the probability of producing first and second-class plates? - Academy 23151
There are 180 pupils in the first year of the academy. Seven girls for every five boys, so there are how many girls in the year? - Probability
How probable is a randomly selected three-digit number divisible by five or seven? - The coal
The coal stock would be enough to heat a larger room for 12 weeks and a smaller one for 18 weeks. It was heated for four weeks in both rooms, then only in the smaller one. Thus, the coal stock was enough for how long? - The right triangle
The right triangle ABC has a leg a = 36 cm and an area S = 540 cm². Calculate the length of the leg b and the median t2 to side b. - Concentric circles and chord
In a circle with a diameter d = 10 cm, a chord with a length of 6 cm is constructed. What radius has the concentric circle while touching this chord?
- The hollow cylinder
The hollow cylinder has a height of 70 cm, an outer diameter of 180 cm, and an inner diameter of 120 cm. What is the body's surface, including the area inside the cavity? - Cllub flag
The children had the club flag sewn on. The red color covered 2/20 of the flag's total area, the blue area a fifth, and the yellow 19% of the entire area. What percent is the green area occupied? - The four
The four pirates divided 65 coins into each other. They were sorted by age, the youngest receiving the least number of coins, each half more than the previous one. How many coins did the oldest pirate receive? - In a
In a triangle, the aspect ratio a: c is 3:2, and a: b is 5:4. The perimeter of the triangle is 74cm. Calculate the lengths of the individual sides. - Five letters
How many ways can five letters be arranged?
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