Maths practice for 13 year olds - page 323 of 331
Number of problems found: 6604
- Rectangular cuboid
The rectangular cuboid has a surface area 5447 cm², and its dimensions are in the ratio 2:4:1. Find the volume of this rectangular cuboid.
One cube is an inscribed sphere, and the other one is described. Calculate the difference of volumes of cubes if the difference of surfaces in 231 cm².
- Pasture 79214
I need to find out the number of bulls in the third period. In the first period, 12 bulls grazed on 3 and 1/3 ha for 4 weeks. In the second period, 21 bulls graze on 10 ha for 9 weeks. How many bulls in the third period graze for 24ha and 18 weeks? The pa
- Identical 32493
Forty identical traffic cones with base diameter d = 36 cm and height v = 46 cm are to be painted orange on the outside (without base). How much do we pay for paint if we need 500 cm³ of paint to paint 1 m² and 1 liter of paint costs CZK 8?
- Two doctors
Doctor A will determine the correct diagnosis with a probability of 89% and doctor B with a probability of 75%. Calculate the probability of proper diagnosis if both doctors diagnose the patient.
- Cuboid-shaped 49763
The cuboid-shaped sheet metal tank with dimensions a=25dm, b=5.6m, and c=180cm will be painted from the outside. How many cans of paint do we need to buy, and how many CZK crowns will we pay? One costs CZK 204, and it is enough to paint 8.5m².
- Pardubická 4651
Jirka decided to divide the winnings from the bet in Velká Pardubická between himself and his three younger brothers according to age in the ratio of 2:3:5:7. They paid each amount in whole crowns. One of the amounts was CZK 679. How big was the win?
From the crossing of two perpendicular roads started two cyclists (each on a different road). One runs at an average speed of 28 km/h, and the second 24 km/h. Determine the distance between them after 45 minutes of cycling.
- Brno-Tachov highway
The distance Brno-Tachov is 360 km. At 8:00 a. M., a car travels from Brno on the highway at an average speed of 90 km/h. An hour later, a vehicle leaves Tachov towards Brno, whose average speed is 110 km/h. Calculate how far apart they will be at 11:00 a
- Sound speed in Earth
Through the surface layers of the Earth, sound propagates 13 times faster than through air. The charge exploded 1.7 km from the measuring station during the geological survey. How long does it take between the vibration of the soil at the measuring point
- Cardboard box
Peter had square cardboard. The length of the pages was an integer in decimetres. He cut four squares with a side of 3 dm from the corners and made a box out of it, which fit precisely 108 cubes with an edge one dm long. Julia cut four squares with a side
- Two rectangles
I cut out two rectangles with 54 cm² and 90 cm². Their sides are expressed in whole centimeters. If I put these rectangles together, I get a rectangle with an area of 144 cm². What dimensions can this large rectangle have? Write all options. Explain your
- Car driver
The car driver is in town A and is scheduled to be in town B at a specified hour. If it travels at an average speed of 50km/h, it will arrive in city B 30 minutes later. But if he travels at an average speed of 70km/h, he would arrive half an hour earlier
- Children pool
The bottom of the children's pool is a regular hexagon with a = 60 cm side. The distance between opposing sides is 104 cm, and the height of the pool is 45 cm. A) How many liters of water can fit into the pool? B) The pool is made of a double layer of pla
- Three friends
Three friend squirrels together went to collect hazelnuts. Zrzecka found more than twice Pizizubka, and Ouska was even three times more than Pizizubka. On the way home, they talked while eating and were cracking her nuts. Pizizubka ate half of all nuts co
The man conducting the census asks a woman the age of three daughters. Woman says when multiplying the age, get the number 72; if their ages add up, get a number of our house, as you see. The man says: That is not enough to calculate their ages. She says:
- Otto and Joachim
Otto and Joachim go through the woods. After some time, Otto becomes tired and makes 15 minutes stop. Joachim, meanwhile, continues at 5 km/h. Otto, when he set off again, first running speed of 7 km/h, but it keep only 30 sec and 1 minute must continue a
- Snowman 2
On the medal, which has the shape of a circle with a diameter 18 cm, is sketched a snowman so that the following requirements are met: 1. snowman is composed of three circles, 2. space over the snowman is the same as under it, 3. diameters of all circles
- Circumference 30781
How many square decimeters of decorative paper are needed to make cone-shaped carnival hats for 46 first-graders if the first-graders head circumference is 49 cm and the cap height is 33 cm? Is it necessary to add 3% paper to the folds?
- Investigation 6024
Kamil saved up to buy a new phone case, which cost CZK 390. He only put ten and twenty crowns in the cash box. After two months of investigation, he had 25 coins in his treasury. When he calculated the total value of all the coins, he found out that he st