Math practice for 13 year olds - page 56 of 419

Number of problems found: 8372

Kilograms 83204
Nine kilograms of bell metal contain 7 kg of copper, the rest of which is tin. How much copper and how much tin were used to cast five bells? Each of the two larger bells weighed 535kg, and each of the remaining three smaller ones weighed 286kg.
Weighing 83201
Bronze is an alloy of copper and tin in a ratio of 1:4. How much copper does a bronze piece of jewelry weighing 25 g contain?
Buy and sell
The selling price is 5.75 EUR, and the buying price is 4 EUR. By what percentage was the price increased?
Construct 83195
Two line segments of different lengths are given. Construct a circle k so that both line segments are its chords.
Seamstresses 83192
Three sewers sew 7 skirts in 15 hours. How many skirts can 2 seamstresses make in 50 hours?
Mathematics 83190
The number of students studying teacher studies in mathematics has decreased in the last twenty years in a ratio of 2:10. How many students are studying teacher studies now when twenty years ago there were 50?
Percentages 83188
There are 10 bags displayed in the store, 2 of which have a hidden error. Buyers randomly choose one bag. Express in percentages the probability that they will buy the bag without a mistake.
The balance - the lever
For the lever to be balanced, the arms' lengths must be inversely proportional to the weight ratio of the weights suspended on these arms. Complete the data: 30 cm, 10 cm, 4 kg, and m₂ kg.
Original model
When drying, the modeling mass loses 36% of its original volume. If the cube's volume is 5.12 dm³ after drying, what was the original length of the edge?
Apprentice 83169
The master gave the apprentice the task of dividing the 28 m long electric cable into two parts so that the second part was 2.5 times larger than the first. How long were the cable sections supposed to be?
Afternoon 83168
In the morning, 6 liters more water was in the green canister than in the blue one. In the afternoon, the gardener poured 1 liter of water from the green canister into the blue one. There was then twice as much water in the green canister as in the blue o
Successful 83167
Eighth-grade test results: 8D =? 8B = 47 8A = 44 8E = 37 8C = 28 Class 8A achieved exactly the average result. How many points did the winning class 8D get? By what % is class 8B more successful than class 8C?
Increased number
A farmer has 250 cows. One cow has 5m² in the cowshed. When their number increases by 26, how much m² will the space for one cow decrease?
Enlarges 83161
Enlarges the number 148 in a ratio of 13:4
Overhangs 83158
The area of a right triangle ABC is 346 cm², and the angle at vertex A is 64°. Calculate the lengths of the overhangs a and b.
Hypotenuses 83154
In a right-angled triangle ABC with a right angle at the vertex C, the magnitudes of the hypotenuses are given ta=5, tb=2√10. Calculate the side sizes of triangle ABC and the circle's radius described by this triangle.
Circumscribed 83152
Given is an isosceles triangle whose base is 8 cm, and the sides are 15 cm long. Calculate the area of the triangle and the radius of the inscribed and circumscribed circle.
Students 83149
There are 30 students in the class. Five had a mark three — other twos and ones. The average grade was 1.9. How many students got mark one?
Braking 83146
A car of mass m=1t moves at a speed v0=54 km/h. What braking force must be exerted to bring the car to a stop in 10 seconds, and how far will the car travel in this time?
Tetrahedron 83144
A container shaped like a rotating cylinder with a base radius of 5 cm is filled with water. If a regular tetrahedron with an edge of 7 cm is immersed in it, how much will the water level in the container rise?

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