Math practice for 13 year olds - page 78 of 414
Number of problems found: 8276
- Fraction addition division
Add one-third to five-eighths and divide the result by the sum of the numbers five-quarters and two-thirds. - Number double reduced
It is necessary to determine the number whose double is reduced by 15 equals the number 5. - Puzzle wood density
The picture puzzle made of wooden cubes weighs 0.792 kg. One cube has an edge length of 4 cm and a weight of 33 grams. Find out how many cubes make up a puzzle and calculate the wood density in kg/m³. - Gunpowder component mixture
Gunpowder is made from a mixture of coal, sulfur, and lignite, with 4 times more lignite than sulfur and 3 times more sulfur than coal. Calculate how many kilograms of individual components are needed to produce 240 kg of gunpowder.? - Natural number sum
Calculate the sum of the squares of single-digit natural numbers less than 6 - Wreath cream price
Eve paid €8.4 for three wreaths and five creams. Jane paid €15.6 for 9 wreaths and 7 creams. How much will Jane pay for one wreath and one cream? - Three ratios
Calculate x in terms of: x:7=6:4 1/2:x=5:3/4 4:3=8:x - Pupil number decrease
Over five years, the number of pupils in the school decreased from 455 to 335. By what percentage did the number of pupils decrease? - Dress double discount
Dresses that initially cost 100 € after a double discount of 10% subsequently increased in price by 20%. How much did they cost? - Spherical layer volume
Sketch a spherical layer formed from a sphere with a radius of r= 8.5 cm, given: v=1.5 cm, r1=7.7 cm, r2=6.8 cm. What is its volume? - Class boy girl
There are 32 children in the class. If there were three more boys and one less girl, there would be an equal number of girls and boys in the class. How many boys are there in the class? - Savings ratio three
The savings of Victor and Peter are in the ratio of 15:8, and the savings of Peter and George are in the ratio of 2:1. What is the ratio of the savings of Victor, Peter, and George? - Plate glass ratio
5 out of 32 plates and 2 out of 20 glasses were broken at the party. What is the ratio of plates to glasses now? - Pavel Vojta trees
Paul and Victor were planting trees at a forestry work camp. Paul planted two more trees than Victor in each six-hour shift. Together, they planted 156 saplings in three shifts. How many saplings did each of them plant? - Diamond tile paving
How many diamond-shaped tiles with a side of 25 cm and a height of 20 cm are needed to pave a rectangular courtyard with sides of 30 m and 28 m if the joints represent 1/20 of the area? - Mr. Quick
Mr. Rychlý needs to drive from Brno to Prague. There is an oversized load on the D1 motorway, which leaves Brno at 11:00 p.m. at a speed of 12 km/h. What is the latest time Mr. Rychlý can depart to avoid getting caught behind the load, i.e. to reach the H - Decorations - spherical
The glass Christmas decorations have the shape of a ball with a diameter of 8 cm. In a small family business, they produce 50,000 pieces a year. The entire surface of these balls is covered with glitter. 400 g of glitter is needed to cover an area of 1 m² - Body mass work
What was the body's mass when it moved along a path of 70 dm and did 1.4 kJ of work? - Diode forward resistance
What is the value of the resistance of the rectifier diode in the forward direction if the current IF = 5 A flows through it and the voltage between the anode UF = 820 mV? - LED series resistor
How big a series resistor do we need to connect to the LED if a voltage drop of 3.2 V is to be created on it and a current of 16 mA flows through the diode? We want to connect the diode to a voltage of 5 V.
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