# Examples for 7th grade (seventh) - page 22

1. 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.
2. Squaring the Circle Calculating side of the square with the same area as the circle of radius 18.
3. Pool coating How many pieces of tiles 25 cm × 15 cm need to coat the bottom and side walls of the pool with bottom dimensions 30 m × 5 m, if the pool can fit up to 271500 liters of water?
4. The professor's birthday Professor of mathematics had 57 birthdays. The director congratulated him. The professor asked the director: "And how old are you?" The director replied: "I'm exactly twice as many years than you were when I was old as to you today." How old is the direc
5. Cube wall Calculate the cube's diagonal diagonal if you know that the surface of one wall is equal to 36 centimeters square. Please also calculate its volume.
6. Carbon dioxide Calculate how many grams of oxygen are in 50 g of carbon dioxide CO2. Relative atomic mass of oxygen is 16 and of carbon is 12.
7. Similarity of squares The ratio of the similarity of the squares ABCD and KLMN is 2.5. Square KLMN area is greater than area of a square ABCD with side a: ?
8. Again saw From the trunk of the tree we have to a sculpture beam with rectangular cross-section with dimensions 146 mm and 128 mm. What is the trunk smallest diameter?
9. Pumps 3 Two pumps of the same power fill the garden pool for 10 hours. How many of these pumps would have to use if we want to shorten the filling of the pool to four hours?
10. Forest nursery In Forest nursery plant one pine to 1.9 m2. Calculate how many plants are planting in area 362 acres.
11. Clock What distance will pass end of 8 cm long hour hand for 15 minutes? 8.3 meters long ladder is leaning against the wall of the well, and its lower end is 1.2 meters from this wall. How high from the bottom of a well is the top edge of the ladder?
13. Pennies 800 pennies have the same value as 100 ducats. 100 pennies have the same value as 250 tolars. How many ducats has the same value as 100 tolars?
14. Rising price The book first become more expensive by 5 euros. New price was later increased by 8%. After the second price increase book cost 46 euros. What was the original price of the book?
15. Water tank 2 Water tank cuboid is 12 meters long and 6.5 meters wide and 1.2 meters high. How many hectoliters are in the tank when it is filled to 81%?
16. Logik game Letter game Logik is a two player game, which has the following rules: 1. The first player thinks five-letter word in which no letter is not repeated. 2. The second player writes a five-letter word. 3. The first player answers two numbers - the first numbe What size have angles in quadrilateral (4-gon) if they are in a ratio of 8: 9: 10: 13? Practitioners lined up in rectangle with row with four, five or six exercisers, one always missing to full rectangle. How many exercisers were on the field, if they have estimated not been more than 100? Plane shape has a maximum area 677 mm2. Calculate its perimeter if perimeter is the smallest possible. Passenger car travels 1 km for 2.3 minutes, a truck during a 50 seconds long. How much is the speed of the truck less?