# Expression of a variable from the formula - 7th grade (12y) - math problems

#### Number of problems found: 238

- Surface of cuboid

Find the surface of the cuboid if its volume is 52.8 cm^{3}and the length of its two edges is 2 cm and 6 cm. - 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 - Six painters

Six painters paint an area of 120 m^{2}in 4 hours. How long does it take for 12 painters to paint 480 m^{2}with the same performance? - What is bigger?

Which ball has a larger volume: a football with a circumference of 66 cm or a volleyball with a diameter of 20 cm? - Extending square garden

Mrs. Petrová's garden had the shape of a square with a side length of 15 m. After its enlargement by 64 m^{2}(square), it had the shape of a square again. How many meters has the length of each side of the garden been extended? - Cone and the ratio

Rotational cone has a height 23 cm and the ratio of the base surface to lateral surface is 7: 9. Calculate a surface of the base and the lateral surface. - Oil tank and pipes

The underground oil tank can be filled by two oil pipelines. The first is filled in 72 hours and the second in 48 hours. How many hours from the moment when first pipeline began to fill the oil is it necessary to start filling it with the second to fill i - Theater

The theater has in each row with 19 seats. Ticket to the first 10 rows is for 30 USD. In the next rows is for 15 USD. The theater was completely sold out. Revenue was 12255 USD. How many rows are in the theater? - A map

A map with a scale of 1: 5,000 shows a rectangular field with an area of 18 ha. The length of the field is three times its width. The area of the field on the map is 72 cm square. What is the actual length and width of the field? - On the farm

On the farm were housed 70 heads of cattle with food supply for 180 days. After 60 days, 10 head of cattle sold, and for the next 30 days they sold 10 more. How many days is sufficient supply of feed for the remaining cattle? - Book reading

If we read the book at a speed of 15 pages a day, we read it 3 days before we read it at a speed of 10 pages per day. If I read at 6 pages per day, how many days will I read the book? - Cube containers

Replace the two cube-shaped containers with 0.8 dm and 0.6 dm edges with a single cube-shaped one so that it has the same volume as the two original ones together. What is the length of the edge of this cube? - Three pumps

The water tank is emptied with the first pump in 6 hours, with the second pump in 2 hours. In order to be emptied in 1 hour, all three pumps had to be started at once. How long will take tank be emptied by only the third pump? - Two machines

Performances of two machines are in a ratio of 7:12. A machine with less power produced 406 pieces of products per shift. a) How many pieces produced per shift second machine? b) How many pieces produced two machines together for five shifts? - Orchard

One-eighth of the trees in the fruit plant in winter froze and one-twelfth of damaged disease and pests. Healthy trees remained 152. Is it enough to supply 35 trees to restore the original number of trees in the orchard? - Cone

Circular cone of height 15 cm and volume 5699 cm^{3}is at one-third of the height (measured from the bottom) cut by a plane parallel to the base. Calculate the radius and circumference of the circular cut. - Prism height

What is the height of the prism with the base of a right triangle with 6 cm and 9 cm? The diaphragm is 10.8 cm long. The volume of the prism is 58 cm^{3}. Calculate its surface. - IS trapezoid

Calculate the length of diagonal u and height v of isosceles trapezoid ABCD, whose bases have lengths a = |AB| = 37 cm, c = |CD| = 29 cm and legs b = d = |BC| = |AD| = 28 cm. - 3sides prism

The base of vertical prism is an isosceles triangle whose base is 10 cm and the arm is 13 cm long. Prism height is three times the height of base triangle. Calculate the surface area of the prism. - Floating of wood - Archimedes law

What will be the volume of the floating part of a wooden (balsa) block with a density of 200 kg/m3 and a volume of 0.02 m^{3}that floats in alcohol? (alcohol density is 789 kg/m3)

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