Math practice for 13 year olds - page 368 of 423
Number of problems found: 8454
- Bronze, tin and copper
Bronze is an alloy of tin and copper. An alloy of 10% tin and 90% copper is Gunmetal. It is bell metal if it contains 20% tin and 80% copper. How many tons of molten bell metal and copper are needed to make 100 tons of Gunmetal? - Two tributaries
Two tributaries of the pool fill it in 10 hours. One of the tributaries would fill 15 hours. How long would fill the first tributary? - Rectangle - sides 4
The perimeter of the rectangle is 72 cm. Calculate the length of the sides that are in the ratio of 3:5. - Cubes
How many cubes with an edge length of 5 cm may fit in the cube with an inner edge of 0.4 m maximally? - Circumference 2489
The circumference of Baikal in km is the number b, which must be added to the empty space in the equation below so that its solution is x = 12,000. (x / 30) + (x / 20) = x - ………… Thanks - Tree trunk
From the tree trunk, the diameter at the narrower end is 28 cm, and a beam of the square cross-section is to be made. Calculate the longest side of the largest possible square cross-section. - Similarity of squares
The ratio of the similarity of the squares ABCD and KLMN is 2.5. Square KLMN area is greater than an area of a square ABCD with side a: ... - Calculate 2482
The train left Košice at 2:45 PM to Poprad, 120 km away. At 5:45 PM, we met in Poprad with an oncoming train from Žilina, 140 km from Poprad. Calculate what time the train left Žilina if you know that it was 8 km/h faster than the train from Košice. - Cyclist vs boat
The cyclist wants to ride a short distance by boat, but when he stops at the pier, the boat does not pick up passengers yet and is preparing to leave. The cyclist decides that the ship will catch up at the next stop. The stop is 12km far along the water a - Truck and car
At 6h45min, the truck started at a speed of 36 km/h. At 7h30m behind it, a passenger car. Find the passenger car's average speed to catch the truck 72 km away from the factory. - Electronics 2476
The electronics store offers a TV with a diagonal screen of 33 inches; the screen's height (without borders) is 44 cm. How wide is the TV if the edge on each side of the screen is 1.1 cm? - Increased 2472
The price of skis increased twice from May to December, always by 20%. In December, the skis cost 1440 SKK. What was the original price in May? - Candies - splitting
Danka and Janka split a pack of candies in a ratio of 5:7. Jana received four more candies than Danka. How many candies were in the package? - Two aircraft
Two planes fly to the airport. At some point, the first airplane is away from the airport by 98 km and the second by 138 km. The first aircraft flies at an average speed of 420 km/h, and the second average speed is 360 km/h, while the tracks of both plane - Savings 2
Jozef and Michael saved 46 euros together. Michael saved 22 euros more than Jozef. How much did they save each of them? - Sprinter
Sprinter runs the relay 4 x 400 m to the handover at a 42 km/h speed. A second runner is at the start of the handover area 20 m long and runs when it is the first sprinter at a distance of 10 m. Calculate the speed at which the second runner must run to t - Cork and swimming
If a person weighs 80 kg, how many kilograms of cork must take a swimming belt to float on water? The density of the human body is 1050 kg/m3, and the cork is 300 kg/m³. (Instructions: Let the human body and cork on a mixture with a density of - Students 2462
There are five girls and five more boys in the class. How many students are in the class? - Children 2461
On the slope were k=60 skiers. How many adults are on the hill if children are skiing 15? - Is right?
Determine whether the triangle with legs (catheti) 19.5 cm and 26 cm and the length of the hypotenuse 32.5 cm is rectangular.
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