# Expression of a variable from formula - examples - page 24

- Girls

The boys and girls in the class formed without the rest of the fives, 2 girls and 3 boys. There are 6 girls missing to create mixed pairs (1 boy and 1 girl). How many girls are in the classroom? - Geometric progression

In geometric progression, a1 = 7, q = 5. Find the condition for n to sum first n members is: sn≤217. - Isosceles trapezium

Calculate the area of an isosceles trapezium ABCD if a = 10cm, b = 5cm, c = 4cm. - Perimeter of base

The circumference of the base of the rotating cylinder is same as its height. What is the diameter and height of this cylinder with volume 1 liter? - Spherical tank

The tank of a water tower is a sphere of radius 35ft. If the tank is filled to one quarter of full, what is the height of the water? - Square root 2

If the square root of 3m^{2}+22 and -x = 0, and x=7, what is m? - Meat loses

Meat loses 18% of its weight by smoking. How much raw meat butcher used to manufacture 35 kilos of smoked? - Cylinder height

Calculate the height of the cylinder and its surface is 2500 dm^{2}and the bases have a diameter 5dm. - 3d printer

3D printing ABS filament with diameter 1.75 mm has density 1.04 g/cm^{3}. Find the length of m = 5 kg spool filament. (how to calculate length) - Rectangle diagonal

The rectangle, one side of which is 5 cm long, is divided by a 13 cm diagonal into two triangles. Calculate the area of one of these triangles in cm^{2}. - Square

Calculate the area of the square shape of the isosceles triangle with the arms 50m and the base 60m. How many tiles are used to pave the square if the area of one tile is 25 dm^{2}? - Expressions 3

If k(x+6)= 4x^{2}+ 20, what is k(10)=? - Diagonals of pentagon

Calculate the diagonal length of the regular pentagon: a) inscribed in a circle of radius 12dm; b) a circumscribed circle with a radius of 12dm. - Motorcyclist

From Trutnov, the motorcyclist started at an average speed of 60km/hour. At 12.30hrs the passenger car was started at a speed of 80km/hour. How many hours and at what distance from Trutnov will car catch a motorcycle? - Simple equations

Solve system of equations: 5x+3y=5 5x+7y=25 - Clothes

Danka and Janka collect clothes. Danka had 9 more than Janka, so she gave her 7. Which now has more cloth and how many? - SSA and geometry

The distance between the points P and Q was 356 m measured in the terrain. The PQ line can be seen from the viewer at a viewing angle of 107° 22 '. The observer's distance from P is 271 m. Determine the viewing angle of P and observer. - Summer tires

Three tire servants have to change the summer tires on 6 cars in 2 hours. Mark's replacement would take 4.5 hours, Jirka would do it in 3 hours and 10 minutes, and Honza in 4 hours. Will they be able to replace all tires at the desired time? - The price

The price of the land increased by 17%. What was the original price of the land if it now costs 46800 €? - A truck

A truck departs from a distribution center. From there, it goes 20km west, 30km north and 10km west and reaches a shop. How can the truck reach back to the distribution center from the shop (what is the shortest path)?

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