# Examples for 8th grade - page 90

1. Conical area A right angled triangle has sides a=12 and b=19 in right angle. The hypotenuse is c. If the triangle rotates on the c side as axis, find the volume and surface area of conical area created by this rotation.
2. Two boats The sightseeing boat sail at 25 km / h. The cruise take 6 hours. How long the another boat sails at 60 km/h?
3. Drying apples By drying, apples lose 85% of their weight. How many kgs of dried apples do we get from 820 kilograms of fresh?
4. Pumping The tank is filled with a larger pump in 12 hours and with scond pump in 15 hours. For how long does the tank fill when both pumps are switched on at the same time?
5. Two lands The common area of the two neighboring lands is 964 m2. The second land is 77 m2 smaller than twice the size of the first land. Find the areas of each land.
6. Three granaries Three granaries hold 7,800 metric cent (q) of grain. In the first, 70 tonnes of grain was more than the second and in the third it was 120 tonnes less than in the second. How many grain were in each granary?
7. Diver and pressure Determine what pressures is exposed diver without a suit at a depth of 15 meters, with a small space suit at a depth of 25 meters and a massive suit at a depth of 70 m in water. The ladder has a length 3.5 meters. He is leaning against the wall so that his bottom end is 2 meters away from the wall. Determine the height of the ladder.
9. Years Susan is 3 years and as she will be old as Teodor now him will be 11. How old is Teodor today?
10. Chord It is given to a circle k(r=6 cm) and the points A, B such that / AB / = 8 cm lies on k. Calculate the distance of the center of circle S to the midpoint C of the segment AB.
11. Weightlifter Weightlifter lifted 75% of its weight. Determine how much weight lifted when he weighs 132 kg.
12. Forces on earth directions A force of 60 N [North] and 80 N [East] is exerted on an object wigth 10 kg. What is the acceleration of the object?
13. Hexagon area The center of the regular hexagon is 21 cm away from its side. Calculate the hexagon side and its area.
14. The gardener The gardener bought trees for 960 CZK. If every tree were cheaper by 12 CZK, he would have gotten four more trees for the same money. How many trees did he buy?
15. Cancer Of the 80 people 50 people ill cancer. What percentage of people isn't ill? The double ladder has 3 meters long shoulders. What is the height of the upper of the ladder reach if the lower ends are 1.8 meters apart?
17. Shots Determine the percentage rate of keeper interventions if from 32 shots doesn't caught four shots.
18. Walkers Walker, which makes 120 steps per minute, make distance from point A to point B for 55 minutes. The length of his step is 75cm. For how long does this distance go boy who will do 110 steps 60 cm long in a minute?
19. Working time At 10 hours work shift, work is done in 16 days. How many days will the work be done at 8 hours shifts? Calculate how many percent will increase the length of an HTML document, if any ASCII character unnecessarily encoded as hexadecimal HTML entity composed of six characters (ampersand, grid #, x, two hex digits and the semicolon). Ie. space as: &#x20;