# Expression of a variable from formula - examples - page 13

1. Family
Son is 3/5 smaller than the mother. Mother is 99 cm higher than the son. How tall is the mother?
2. Axial cut
The cone surface is 388.84 cm2, the axial cut is an equilateral triangle. Find the cone volume.
3. Orchard
3/5 of the trees in the orchard are apples, 1/3 are cherries and the remaining five trees are pear. How many trees are in the orchard?
The ladder is 10 m long The ladder is 8 m high How many meters is the distant heel from the wall?
5. Apples 5
In six crates are 45 kg of apples. In five crates were the same amounth and in one crate was 3 kg of apples more. How many kg of apples were in each crate?
6. Three children
3 children eat 8 chocolates in 6 days. How many chocolates 6 children eat in 18 days?
7. Calf
The weight of the calf meat obtained is 65% of the total weight of live calves. What was the weight of a calf from which 285 kg of meat was obtained?
8. Cuboid
Cuboid has a surface of 516 cm2. Side a = 6 cm and b = 12 cm. How long is the side c =?
9. Midpoints
Triangle ABC with sides a = 5 cm, b = 3 cm, c = 40mm has a midpoint of K, L, M. How many centimeters is long perimeter of parallelogram KBLM?
10. Difference AP
Calculate the difference of arithmetic progression if the sum of its first 19 members Sn = 8075 and the first member is a1 = 20
11. Chairs
Determine the number of seats in the seventh row and ninth row, if 3rd row has 14 seats and in every next row of seats has five more than the previous row.
12. Wall height
Calculate the surface and volume of a regular quadrangular pyramid if side a = 6 cm and wall height v = 0.8dm.
13. Truncated cone 3
The surface of the truncated rotating cone S = 7697 meters square, the substructure diameter is 56m and 42m, determine the height of the tang.
14. Circle's chords
In the circle there are two chord length 30 and 34 cm. The shorter one is from the center twice than longer chord. Determine the radius of the circle.
15. Euros
Peter spent a quarter of his pocket saving. He has 9 euros now in his wallet . How many euros spent?
16. Cyclist vs boat
The cyclist wants to ride a short distance by boat, but when he stops at the pier, the boat does not pick up passengers yet and is preparing to leave. The cyclist decides that the boat will catch up at the next stop. The stop is 12km far along the water an
17. Apples 2
Dried apples contain 15% water. Fresh apples contain 80% water. How many kg of apples we need buy in order to get 3 kg of dried apples?
18. Diagonals of a rhombus
One of the diagonals of a rhombus is twice as the other. If the sum of the lengths of the diagonals is 24, find the area of the rhombus.
19. Four integers
Fnd four consecutive integers so that the product of the first two is 70 times smaller than the product of the next two.
20. Arm-leg
Calculate the length of the base of an isosceles triangle with a circumference 224 cm if the arm length is 68 cm.

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