# Examples for 8th grade - page 80

1. Body diagonal
Find the cube surface if its body diagonal has a size of 6 cm.
Find the volume and surface of a regular quadrilateral pyramid if the bottom edge is 45 cm long and the pyramid height is 7 cm.
3. Reciprocal equation
Determine the root of the equation: 9/x-7/x=1
4. Conva
How many liters of water fit into the shape of a cylinder with a bottom diameter 20 cm and a height 45 cm?
5. Garden
The garden has a rectangular shape with lengths of 25 and 40 meters. It has been expanded so that each of its size increased by one fifth. How many square meters increased its acreage?
6. Potatoes 6
The farmer brought potatoes to the market. In the first hour he sold two-fifths of the potatoes brought, in the second hour he sold five-sixth of the remaining potatoes, and in the third hour he had sold the last 40kg of potatoes. How many kg of potatoes d
7. Masons
1 mason casts 30.8 meters square in 8 hours. How long casts 4 masons 178 meters square?
The ladder is 10 m long The ladder is 8 m high How many meters is the distant heel from the wall?
9. Remuneration
Total remuneration for workers is 47 000 CZK. The second worker received 20% more than the first and third 4000 CZK less than a second employee. How many CZK each received?
10. Failure
Drivers of passenger cars have calculated that at a speed of 60 km/h arrives at destination within 40 minutes. After 20 km refrain five minutes due a technical failure. How fast must go the rest of the way to the finish came at the scheduled time?
11. Krkonose CZ
Tourist's rod on the tourist route in the Krkonose was 1/5 of its length into the ground. Snow fell in winter and 1/3 of the length of the rod remained above the snow. Find the height of the snow if the length of the part above the snow is 32 cm greater t
12. Iron cast
What is the weight of cast iron with volume 3575 cubic centimeters. The density of the cast iron is 7600 kg/m3
13. Sum of three numbers
The sum of three numbers from which second number is 20% smaller than the first number and the third number is 25% smaller than the second number is 96. Determine this numbers.
14. Two circles
Two circles with a radius 4 cm and 3 cm have a center distance 0.5cm. How many common points have these circles?
15. Two ages
Gabrielle is 9 years younger than Mikhail. The sum of their ages is 87. What is Mikhail's age?
16. Ice cream
Annie likes much ice cream. In the shop are six kinds of ice cream. In how many ways she can buy ice cream to three scoop if each have a different flavor mound and the order of scoops doesn't matter?