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

1. Sales off
The price has decreased by 20%. How many percents do I have to raise the new price to be the same as before the cut?
2. Rectangular garden
The sides of the rectangular garden are in ratio 1: 2. The diagonal has a length of 20 meters. Calculate the area and perimeter of the garden.
3. Two resistors
Two resistors when they give 25 ohms in series and 4 ohms in parallel what the values of
4. Edges or sides
Calculate the cube volume, if the sum of the lengths of all sides is 276 cm.
5. The pot
The pot is a cylinder with a volume of V = 7l and an inner diameter of d = 20cm. Find its depth.
6. Diagonals of the rhombus
How long are the diagonals e, f in the diamond, if its side is 5 cm long and its area is 20 cm2?
7. A cylinder
A cylinder 108 cm high has a circumference of 24 cm. A string makes exactly 6 complete turns around the cylinder while its two ends touch the cylinder's top and bottom. (forming a spiral around the cylinder). How long is the string in cm?
8. 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?
9. Guppies
Audrey has some guppies in a fish tank. The ration of the oranges guppies to silver guppies is 3:5. She has 12y oranges guppies. Write the number of silver guppies she has in terms of y
10. Deviation of the lines
Find the deviation of the lines AG, BH in the ABCDEFGH box-cuboid, if given | AB | = 3cm, | AD | = 2cm, | AE | = 4cm
11. Final exam
There are 5 learners in a class that has written a final exam Aleta scored 55% vera scored 36% and Sibusiso scored 88% if Thoko scored 71% and the class average was 63%. What was Davids score as a percentage?
12. 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?
13. Isosceles trapezium
Calculate the area of an isosceles trapezium ABCD if a = 10cm, b = 5cm, c = 4cm.
14. Geometric progression
In geometric progression, a1 = 7, q = 5. Find the condition for n to sum first n members is: sn≤217.
15. 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?
16. Calculate
Calculate the length of a side of the equilateral triangle with an area of 50cm2.
17. Pilot
How high is the airplane's pilot to see 0.001 of Earth's surface?
18. KLMN trapezoid
The KLMN trapezoid has bases KL 40cm and MN 16cm. On the KL base is point P. The segment NP divides the trapezoid into units with the same area. What is the distance of point P from point K?
19. Meat loses
Meat loses 18% of its weight by smoking. How much raw meat butcher used to manufacture 35 kilos of smoked?
20. Square root 2
If the square root of 3m2 +22 and -x = 0, and x=7, what is m?

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