# Examples for 8th grade - page 89

1. Efficiency
What is the power output of kettle 2 kW with efficiency 90%?
2. Cube 1-2-3
Calculate the volume and surface area of the cube ABCDEFGH if: a) /AB/ = 4 cm b) perimeter of wall ABCD is 22 cm c) the sum of the lengths of all edges of the cube is 30 cm.
3. Working together on project
Two employees working on the project. First make it alone for 20 days the second for 24 days. How many days will take to complete project if 5 days they work together then first will take two days holiday and after returning they completes a project toget
4. Price increase
A 20 percent price increase meant a 90-crown raise. How many cost a product after?
5. Cylindrical tank
Cylindrical tank holds 600hl water and is deep 2.5 m. Calculate the diameter of the cylinder.
6. A mast
A mast 32 meters high was broken by the wind so that its top touches the ground 16 meters from the pole. The still standing part of the mast, the broken part and the ground form a rectangular triangle. At what height was the mast broken?
7. Volume increase
How many percent will increase in the pool 50 m, width 15m if the level rises from 1m to 150cm?
8. Rhombus MATH
Construct a rhombus M A T H with diagonal MT=4cm, angle MAT=120°
9. Plane II
A plane flew 50 km on a bearing 63degrees20 and the flew on a bearing 153degrees20 for 140km. Find the distance between the starting point and the ending point
10. Boys and girls
There are 48 children in the sports club, boys are 10 more than girls. How many girls go to the club?
When Ben is so many years old to Adam today, Adam will be 23 years old. When Adam was as old as Ben, Ben was two years old. How old is today Ben and Adam?
12. Cargo
Car with cargo weight 7610 kg. Weight of car is 23% of the total weight of car and cargo. How heavy is cargo?
13. Schools
Three schools are attended by 678 pupils. To the first attend 21 students more and to the third 108 fewer students than to second school. How many students attend the schools?
14. Rectangular triangle PQR
In the rectangular triangle PQR, the PQ leg is divided by the X point into two segments of which longer is 25cm long. The second leg PR has a length 16 cm. The length of the RX is 20 cm. Calculate the length p of side RQ. The result is round to 2 decimal
15. Money duo
Julius and Mark have together 45 euros. Mark has 50% more money than Julius. Determine the amount of money that have Mark and Julius.
16. Time gone
Square of Richard age equals the age of his mother. When he will bw two times older then his mom will be 7/2 times older than he. How old is Richard and his mom?