# Examples for 8th grade - page 104

1. Line segment The 4 cm long line segment is enlarged in the ratio of 5/2. How many centimeters will measure the new line segment?
2. Seawater Seawater has a density of 1025 kg/m3, ice 920 kg/m3. 8 liters of seawater froze and created a cube. Calculate the size of the cube edge.
3. Digit sum How many are three-digit numbers that have a digit sum of 6?
4. Square Square JKLM has sides of length 24 cm. Point S is the center of LM. Calculate the area of the quadrant JKSM in cm2.
5. Height as diameter of base The rotary cylinder has a height equal to the base diameter and the surface of 471 cm2. Calculate the volume of a cylinder.
6. Bricklayers Seven bricklayers will build the house in 630 days. How many bricklayers do we need to take after 150 days to complete the building for (additional) 336 days?
7. Sales off The price has decreased by 20%. How many percents do I have to raise the new price to be the same as before the cut?
8. Circular arc Calculate the length of the circular arc if the diameter d = 20cm and the angle alpha = 142 °
9. Highway tunnel The highway tunnel was built from two ends in the north-south direction. The average daily performance of the "northern party" rasters was higher than the average daily power of the "southern party" of the rasters. After 55 business days, both parties met.
10. Three 43 Three brothers inherited a cash amount of 62,000 and they divided it among themselves in the ratio of 5:4:1. How much more is the largest share than the smallest share?
11. Acid evaporation How many kilograms of water do we have to evaporate from 100 kg of 32% acid to make it 80% concentration?
12. Sweater Dana confuses sweater and wool has a choice of seven colors. In how many ways she can choose from three colors to the sleeves?
13. The pot The pot is a cylinder with a volume of V = 7l and an inner diameter of d = 20cm. Find its depth.
14. Water reservoir One drain hole emptied the water from the tank for 20 hours, with the second drain for 30 hours. How long will the water drain from this tank if we open two drains simultaneously?
15. Triangles Hanka cut the 20 cm long straws into three pieces each piece had a length in cm. Then, with these three pieces, she tried to make a triangle. a) What circuit has each of the triangles? b) How long can the longest side measure? c) How many different trian
16. The big clock The big clock hands stopped at a random moment. What is the probability that: a) a small hand showed the time between 1:00 and 3:00? b) the big hand was in the same area as a small hand in the role of a)? c) did the hours just show the time between 21:00.
17. Five pupils Five pupils clean 30 chairs one hour before four pupils. How many chairs clean one pupil in 1 hour?
18. How many How many double-digit numbers greater than 30 we can create from digits 0, 1, 2, 3, 4, 5? Numbers cannot be repeated in a two-digit number.
19. Four painters The company sent four painters to paint the school. They should be done in 12 days. After three days, one painter got ill. How long will the remaining painters paint the school?
20. Girls The boys and girls in the class formed without the rest of the fives, 2 girls and 3 boys. There are 6 girls missing to create mixed pairs (1 boy and 1 girl). How many girls are in the classroom?

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