Math practice for 13 year olds - page 155 of 428
Number of problems found: 8558
- Assembly sick worker
Two assemblers with the same daily output were to complete the assembly in 12 days. After 4 days, one of them got sick, and the other finished the assembly in another 16 days. How long would it take everyone to do the assembly by themselves? - Race second probability
Five competitors took part in the race. Jaro was disappointed that he didn't win. Before announcing second place, he calculated the probability of finishing second. What number did he get if he counted correctly? - Resistor
Resistor 1, with a resistance of 100 Ohms, and resistor 2, with a resistance of 400 Ohms, are connected side by side in the circuit. The voltage between the resistor terminals is 80V. a) Draw a circuit diagram and write the entered quantities in it b) Fin - Tree planting workers
Fifty part-time workers planted 5,200 trees in a forest on a weekend brigade the forest in 9 hours. How many more part-timers do they have to lose next time to plant the same number of trees in eight hours? - Average speed
The car drove on one section of the highway for half an hour at a speed of 80 km/h. Then he reduced his speed to 60km/h. It went three-quarters of an hour at a speed of 60 km/h. What was the average speed of the car? - Three-quarters of volume
A cylindrical container is three-quarters full with six liters of water. We dip a cube-shaped body into the container, which sinks to the bottom. The length of the edge of the cube is 13 cm. Decide what happens to the sink after the cube is dipped. - Fire fighting
The cuboid-shaped fire fighting tank is 6 m long and twice as wide. What is the height of the tank if the firefighters fill the empty tank in 0.5 hours with a hose flow rate of 12 liters per second? - Tank water
Forty-eight liters of water are now in the vertical cylinder-shaped water tank. The water reaches a height of 27 cm. After an all-day downpour, water reaches a height of 72 cm. How much water will there be in the tank? - Resistor parallel connection
Two resistors, R1 = 300 ohms and R2 = 600 ohms, are connected next. A voltage of 220V is connected. Determine the total resistance by which we can replace both the electric currents passing through the individual resistors and the electric current passing - Tic-tac-toe
In how many ways could 9 participants of the school round of five-in-a-row win the first three places? - Percentage base finding
From which number 70% is 30? - Chocolate tea price
Two chocolates and five teas cost a total of 498 CZK. Chocolate is 18 CZK more expensive than tea. How much do one chocolate and one tea cost? - 25 pupils
Twenty-five pupils attend the school dance group, which is 5 percent of all pupils. The judo class is attended by 20 pupils, a quarter of whom also attend a dance group. How many schoolchildren do not go to a dance or judo group? - Beetle spider collection
Mr. Smith has 49 specimens of beetles and spiders in his collection. He needs to remember how many bugs and spiders he has, but he knows he has 324 legs in his collection. How many bugs and spiders does he have in his collection? (Hint: First, figure out - Candy mixture price
They want to buy a mixture of candies for the confectionery, which consists of fruit candies at CZK 170/kg and chocolate candies at CZK 240/kg. The mixture should be 20 kg for 212 CZK/kg. How many fruit candies and how many chocolate candies must he buy? - Pucks
The coach went to buy balls and pucks for his charges. He paid CZK 1,464 for 21 balls and 30 pucks. But then he found out that this amount would not be enough for him, so he bought nine balls and ten pucks for 536 CZK the next day. How much did one ball c - Sisters savings ratio
Sisters Hanka and Jana have saved a total of 560 CZK. A third of Hanka's savings equals a quarter of Jana's savings. How much CZK has Hanka saved, and how much has Jana? - Marble sharing ratio
Four boys shared 100 marbles. The second received 20% more than the first, the third received 20 more bullets than the first, and the fourth received 0.8 times more bullets than the first. How many marbles did each boy get? - Photo height proportion
While photographing the class, Henry noticed that he was only 8 cm tall in the photo, while Patrik standing next to him was 8.5 cm tall. Based on his height, Henry calculated that Patrik must measure 17 dm. How tall is Henry? - Brick lifting work
How many bricks do they have to lift on a 1.2 m high flatbed if I want to do the work 5.88kj and one brick weighs 5 kg?
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