# Expression of a variable from formula - examples - page 17

1. Parallelogram
Calculate the missing side of a parallelogram, if you know the perimeter o and one side: a) o = 7.2 cm; b = 1.8 cm b) o = 5.4 cm; a = 1.9 cm
2. Right triangle eq2
Find the lengths of the sides and the angles in the right triangle. Given area S = 210 and perimeter o = 70.
3. Coefficient
Determine the coefficient of this sequence: 7.2; 2.4; 0.8
4. Inscribed circle
The circle inscribed in a triangle has a radius 3 cm. Express the area of the triangle using a, b, c.
5. Difference AP 4
Calculate the difference of the AP if a1 = 0.5, a2 + a3 = -1.1
6. Volume and area
What is the volume of a cube which has area of 361 cm2?
7. Combinations
If the number of elements increase by 3, it increases the number of combinations of the second class of these elements 5 times. How many are the elements?
8. Boys and girls
There are 28 girls in the hall. 5/7 of all children are boys. How many children and how many boys are there?
9. Trapezium
The area of trapezium is 35 cm2. Find its altitude if the bases are 6cm and 8 cm.
10. Circle chord
Calculate the length of the chord of the circle with radius r = 10 cm, length of which is equal to the distance from the center of the circle.
11. The rope
A 68 centimetre long rope is used to make a rhombus on the ground. The distance between a pair of opposite side corners is 16 centimetres what is the distance between the other two corners?
12. Third member
Determine the third member of the AP if a4=93, d=7.5.
13. Alley
Alley measured a meters. At the beginning and end are planted poplar. How many we must plant poplars to get the distance between the poplars 15 meters?
14. Hexagon cut pyramid
Calculate the volume of a regular 6-sided cut pyramid if the bottom edge is 30 cm, the top edge us 12 cm, and the side edge length is 41 cm.
15. Right triangle from axes
A line segment has its ends on the coordinate axes and forms with them a triangle of area equal to 36 sq. Units . The segment passes through the point ( 5,2). What is the slope of the line segment. ?
16. Solve equation
solve equation: ?
17. Free fall
How long does the stone fall freely into a depth of 80m? What speed will it hit the bottom of the abyss?
18. Three painters
The three painters have painted bridge. The first would work done in 5 days, the second in 6 days, and the third in 7.5 days. How long will the bridge work if they work together?
19. Diagonal
he rectangular ABCD trapeze, whose AD arm is perpendicular to the AB and CD bases, has area 15cm square. Bases have lengths AB = 6cm, CD = 4cm. Calculate the length of the AC diagonal.
20. Area of iso-trap
Find the area of an isosceles trapezoid, if the lengths of its bases are 16 cm, and 30 cm, and the diagonals are perpendicular to each other.

Do you have an interesting mathematical example that you can't solve it? Enter it, and we can try to solve it.

To this e-mail address, we will reply solution; solved examples are also published here. Please enter e-mail correctly and check whether you don't have a full mailbox.