Math practice for 13 year olds - page 228 of 413
Number of problems found: 8260
- Gravitational potential energy
We lift a weight of 2 kg to a height of 50 cm above the top of the table. Determine its gravitational potential energy: a) relative to the tabletop, b) relative to the floor if the table top is 1 m above the floor. - Eight masons
Eight masons will plaster a wall with an area of 1440 m² in 9 days. They work 8 hours a day. How much area will plaster six masons in 4 hours? - Vehicle meeting calculation
The motorcycle left Děčín at an average speed of 40 km/h. At the same time, a passenger car from Prague drove towards him at an average speed of 80 km/h. The distance from Prague to Děčín is about 100 km. How long and at what distance from Děčín will both - Annulus outer radius
An annulus with an area S = 4.2 square meters has an inner radius r = 2.25 m. Determine the outer radius of the annulus. - Where and when
The truck left Kremnica at 11:00 h at a speed of 60 km/h. At 12:30 h, the passenger car started at an average 80 km/h speed. How many kilometers from Kremnica will the passenger car reach the truck, and when? - Ice skates
The price of ice skates was raised twice, first by 25% and then by 10%. After the second price increase, their cost was 82.5 euros. What was the original price of the skates? - Resistor current calculation
At a voltage of 16 V between the ends of the resistor, a current of 200 mA flows through the resistor. What current will flow through the resistor when connected to 48 V? - Appliance current calculation
The measurement showed that a current of 160 mA flows through the appliance at a voltage of 4 V. What current flows through this appliance when connected to a voltage of 12 V? - Parallels and one secant
There are two different parallel lines, a, b, and line c, that intersect the two parallel lines. Draw a circle that touches all lines at the same time. - Flowerbed
We enlarged the circular flower bed, increasing its radius by 3 m. The substrate consumption per enlarged flower bed was nine times greater than before (at the same layer height as before magnification). Determine the original flowerbed radius. - Candy division proof
Mickey got so many candies that all the digits in this number were the same. Prove that whenever he can divide such several candies into 72 equal piles, he can also divide them into 37 equal piles. (Note: candies cannot be broken) - Six students
Two pupils painted the class in four hours. How long will it take for six pupils? - Mixture of nuts
We should prepare the mixture of nuts from almonds, peanuts, and nuts cashew ratio of 1:2:3 (respectively). The price of almonds is 150 CZK/kg, the price of peanuts is 140 CZK/kg, and the price of cashew nuts is 180 CZK/kg. The price of the mixture is det - Ski slope on a map
On a plan with a scale of 1:8000, the ski slope has 12 cm and 0.5 cm lengths. What is the actual piste area in ares? - The trapezium
The trapezium is formed by cutting the top of the right-angled isosceles triangle. The trapezium base is 10 cm, and the top is 5 cm. Find the area of the trapezium. - Blueberries
Five children collect 4 liters of blueberries in 1.5 hours. a) How many minutes do three children take 2 liters of blueberries? b) Eight children will take how many liters of blueberries in 3 hours? - Jacket double discount
The jacket initially cost 80 euros. Then it was discounted twice, always to 80% of the previous price. How much does it cost after the second discount? - Chocolate
Chocolate, which initially cost 1.5 euros, was increased by 40%. How many euros did it cost? - Positional energy What velocity in km/h must a body weighing 60 kg have for its kinetic energy to be the same as its positional energy at the height of 50 m?
- Floating of wood - Archimedes law
Wooden balsa block has a density of 200 kg/m³ and a volume of 0.02 m³ floating in alcohol. Alcohol density is 789 kg/m³. What will be the volume of the floating part of a balsa block?
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