Math practice for 13 year olds - page 175 of 428

Number of problems found: 8558

Hydrogen peroxide solution
Prepare 250g of a 30% solution of hydrogen peroxide in water.
Salicylic acid solution
Prepare 600 g of an 8% solution of salicylic acid.
Blue rock solution
Prepare 100g of a 15% blue rock solution.
Odd number creation
How many odd three-digit numbers can you make of the five cards with the numbers 1, 2, 3, 5, and 6?
Plane distance
Two planes took off from Prague at one point. The first is flying north at a speed of 420 km/h, and the second is flying east at a speed of 560 km/h. How far apart will they be as the crow flies in 25 minutes of flight?
Regular 4-sided pyramid
Find the area (surface area) of a regular 4-sided pyramid if its height is 20 m and the wall height is 23 m.
Clock hand distance
How far apart are the tips of the clock's hands in 3 hours if the larger hand is 124 mm long and the smaller 75 mm?
Cube-shaped container
The cube-shaped container has a height of 52 cm and a square base. The container was filled to the brim with water, and then we immersed a metal cube in it, which caused 2.7 l of water to flow out of the container. After removing the cube from the water,
Bricklayer work
A bricklayer will lay 12 m³ of brickwork in 4 days if he works 7 hours a day. How many days will he lay 51 m³ of masonry if he works 8.5 hours daily?
Rotary motion
Find the orbital time, rotational frequency, and angular rate of the second and minute hands on the watch.
Coat price difference
The blue coat, which costs CZK 1,200, has a price 40% lower than the red coat. What is the price difference between the two coats?
Isosceles + prism
Calculate the volume of the perpendicular prism if its height is 17.5 cm and the base is an isosceles triangle with a base length of 5.8 cm and an arm's length of 3.7 cm.
Lions
If eight lions are 40%, how many would 75% be?
Arm and base
The isosceles triangle has a circumference of 46 cm. If the arm is 5 cm longer than the base, calculate its area.
State name possibilities
If residents of MISSISSIPPI state have to use all the letters to choose their country's name, how many possibilities do they have?
Five-digit number creation
How many 5-digit numbers can we assemble from the numbers 2,3,4,5,6,7,8,9 if each digit can be repeated only once?
Cube volume edge
1. Calculate the volume of a cube whose edge is 3.6 dm long. 2. Calculate the edge's size if you know its surface S = 2166 mm².
Three cubes
Two cube-shaped boxes with edges a = 70 cm; b = 90 cm must be replaced by one cube-shaped box. What will be its edge?
Two ports
Two ships commute along the same route between the ports of Mumraj and Zmatek. They spend negligible time in ports, turn around immediately, and continue sailing. At the same time, a blue ship departs from the port of Mumraj, and a green ship departs from
Coloured numbers
Mussel wrote four different natural numbers with colored markers: red, blue, green, and yellow. When the red number is divided by blue, it gets the green number is an incomplete proportion, and yellow represents the remainder after this division. When it

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