# Examples for 8th grade - page 31

1. SAS triangle The triangle has two sides long 7 and 19 and included angle 36°. Calculate area of this triangle.
2. Exam average Average of marks that have on the certificates students of 8.A class in mathematics is exactly 2.45. If we did not add 1 and 3 of sutdents Michael and Alena, who arrived a month ago, it would average exactly 2.5. Determine how many students have class 8.
3. Mother and daughter Three years ago mother was three times older than daughter. After nine years she will be only twice old. How old is mother (and daughter)?
4. VAT VAT is a tax which the state artificially betrays goods and services for final consumption. VAT in Slovakia is 20%. Calculate how much percent pay less tax residents of Liechtenstein, when VAT is only 8%.
5. Warehouse cars From the warehouse started truck at speed 40km/h. After 1hour 30mins started from the same place same direction a car at speed 70 km/h. For how long and at what distance from the warehouse overtake a truck?
6. Chess How many ways can select 4 fields on classic chess board with 64 fields, so that fields don't has the same color?
7. Suit The suit cost 119 euros. How much cost the pants if it is 50% cheaper than the jacket.
8. Grandfather The grandfather is three years older than an grandmother. The average age of the grandmother, the grandfather and their seven grandchildren is 28 years. The grandchildren have a total of 105 years. Calculate how old is grandfather.
9. Seven-segmet Lenka is amused that he punched a calculator (seven-segment display) numbers and used only digits 2 to 9. Some numbers have the property that their image in the axial or central symmetry was again give some number. Determine the maximum number of three-d
10. Bronze, tin and copper Bronze is an alloy of tin and copper. An alloy of 10% tin and 90% copper is Gunmetal. If it contains 20% tin and 80% copper, it is bell metal. How many tons of molten bell metal and how many tons of copper is needed to make 100 tons of Gunmetal?
11. Gasholder The gasholder has spherical shape with a diameter 20 m. How many m3 can hold in?
12. Sprayers The vineyard can be sprayed first sprayer in 5 hours and with the second in 8 hours. How long would it take if we use sprayers both at once?
13. Rectangle - parallelogram It is given a rectangle that is circumscribed by a circle with a radius of 5 cm. The short side of the rectangle measures 6 cm. Calculate the perimeter of a parallelogram ABCD whose vertices are the midpoints of the sides of the rectangle. The voltage station is every day changing the master password, which consists of three letters. Code generation process does not change and is based on the following procedure: The following letters (A) to (I) correspond to different numbers from 1 to 9. I
15. Work First paver pave pavement for 27 hours. Second for 27 hours. Started first paver and after 4 hours, join the second. How long will they finish pavement?
16. Bath In the bath is 30 liters of hot water. Then added 36 liters of cold water at temperature of 19 °C decreased temperature of water to 41 °C. What was the initial temperature of the hot water?
17. Diamond Side length of diamond is 35 cm and the length of the diagonal is 56 cm. Calculate the height and length of the second diagonal.
18. Painters First painter painted fence himself for 4 hours, the second painter 1.2 hours sooner than first, and the third painters slowest up to 16 hours. How long took them paint fence if worked together?
19. Jan Jan is 13 years and Peter 21 years old. For how many years will their ages in the ratio of 7:9?
20. Paul and Honza Honza went to chat on a bike without a break 4.0 hours. Paul the same way without breaks 50 minutes longer. The difference between the speeds of the two boys was the one kilometer per hour. How fast was Paul, if you know that the speed of the boys did not.

Do you have an interesting mathematical word problem that you can't solve it? Enter it, and we can try to solve it.

To this e-mail address, we will reply solution; solved examples are also published here. Please enter the e-mail correctly and check whether you don't have a full mailbox.

Please do not submit problems from current active competitions such as Mathematical Olympiad, correspondence seminars etc...