# Expression of a variable from formula - examples - page 9

On a weekly forest brigade operates 12 students. After plant one hundred spruces get x CZK, anfter one hundred pines y CZK. How many CZK got one student for one day if planted spruces 25000 and 30000 pines week?
2. Prism
Calculate the height of the prism having a surface area 448.88 dm² wherein the base is square with a side of 6.2 dm. What will be its volume in hectoliters?
3. Cuboid and eq2
Calculate the volume of cuboid with square base and height 6 cm if the surface area is 48 cm2.
4. Inscribed circle
XYZ is right triangle with right angle at the vertex X that has inscribed circle with a radius 5 cm. Determine area of the triangle XYZ if XZ = 14 cm.
5. Rectangle from string
String 12m. Make rectangle when one side is two times longer than its width.
6. Rhumbline
Find circumference and area of the rhumbline ABCD if the short side AD of which has a length of 5 cm, and the heel of the height from D leading to the AB side divides the AB side into two sections of 3 cm and 4 cm.
7. Isosceles right triangle
Contents of an isosceles right triangle is 18 dm2. Calculate the length of its base.
8. Tripled square
If you tripled the length of the sides of the square ABCD you increases its content by 200 cm2. How long is the side of the square ABCD?
9. Ethnicity
Share of ethnicity XY is 26%, which is 1/9 more than in the prewar period. What was the share of that ethnicity in the pre-war period?
10. Right triangle
It is given a right triangle angle alpha of 90 degrees beta angle of 55 degrees c = 10 cm use Pythagorean theorem to calculate sides a and b
11. Rectangle
Perimeter of rectangle is 48 cm. Calculate its dimensions if they are in the ratio 5:3 (width:height)
12. Average speed
When the bus stops at bus stops driving average speed is 45 km/h. If it did not stop it drive at speed 54 km/h. How many minutes of every hour it spend at stops?
13. Cube diagonals
Determine the volume and surface area of the cube if you know the length of the body diagonal u = 216 cm.
14. Interst on savings
The bank offers 1.6% interest. How many euros have to insert at the beginning if we received € 15 on the interest?
15. Cube 5
The surface of the cube is 15.36 dm2. How will change the surface area of this cube if the length of the edges is reduced by 2 cm?
16. Right angled triangle
Hypotenuse of a right triangle is 17 cm long. When we decrease length of legs by 3 cm then decrease its hypotenuse by 4 cm. Determine the size of legs.
17. Car and cyclist
Cyclist started from town at speed 18 km/h. After 1 hour 30 min started the car from town and caught up with the cyclist in 50 minutes. How fast was a car?
18. Value
Determine the value of the following exspressions: a) (23-25)·(4-5) b) (97-123):(18+8)
19. Cube 8
The surface of the cube is 0.54 m2. Calculate the length of the cube edge.
20. Rectangle 3-4-5
The sides of the rectangle are in a ratio of 3:4. The length of the rectangle diagonal is 20 cm. Calculate the content of the rectangle.

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