# Examples for 8th grade - page 101

1. Seamstress The seamstress cut the fabric into 3 parts. The first part was the eighth fabric, the second part was three-fifths of the fabric and the third part had a length of 66 cm. Calculate the original length of the fabric.
2. Sale A camera has a listed price of \$751.98 before tax. If the sales tax rate is 9.25%, find the total cost of the camera with sales tax included.
3. Sugar production From 1 ton of beet, 150 kg of sugar is produced. To clean 1 ton of sugar 450 kg of lime is consumed. Calculate how many kgs of lime is consumed when processing 1 ton of sugar beet?
4. Sale discount The product was discounted so that eight products at a new price cost just as five products at an old price. How many percents is the new price lower than the old price?
5. Our house Our house would paint four painters in 14 days. How long could it paint five painters? How long will it take if two other painters will come to help after 5 days?
6. Regular triangular pyramid Calculate the volume and surface area of the regular triangular pyramid and the height of the pyramid is 12 centimeters, the bottom edge has 4 centimeters and the height of the side wall is 12 centimeters
7. Cuboid The sum of the lengths of the three edges of the cuboid that originate from one vertex is 210 cm. Edge length ratio is 7: 5: 3. Calculate the length of the edges.
8. Birthday Mother bought 21 desserts on the occasion of Mirka's birthday one tips was 9 CZK and the kremlin cost 12 CZK. For all desserts, she paid 213 CZK. How many kremlins and how many tips mums did buy?
9. Average age The company of five people has an average age of 46 years. The average age of the first four is 43 years. How many years has the fifth member of this company?
10. Pendulum Calculate the length of the pendulum that is 2 cm lower in the lowest position than in the highest position. The length of the circular arc to be described when moving is 20cm.
11. Butter At the Orville redenbocher popcorn factory there is a tank of artificial butter substitute which is 55 feet tall and 18 feet in diameter. How many gallons of artificial butter substitute can the tank contain?
12. Exponential equation Determine the value of having y in the expression (3^y): (4^-1)=36.Y is a natural number greater than zero.
13. Bicycle gear The pedal bicycle wheel has 56 teeth and a rear 20 gear tooth. How many times does the bicycle wheel turn when you make 20 turns of the pedal wheel?
14. Harvesters The first harvester will harvest the grain from the field in 20 hours, the second, the more powerful in 10 hours. How long will take harvest this field by both harvesters, if the second harvester has to be set up first and this takes 2 hours? The first har
15. Body diagonal - cube Calculate the surface and cube volume with body diagonal 15 cm long.
16. Quadrangular pyramid The regular quadrangular pyramid has a base length of 6 cm and a side edge length of 9 centimeters. Calculate its volume and surface area.
17. Four numbers The first number is 50% second, the second number is 40% third, the third number is 20% of the fourth. The sum is 396. What are the numbers?
18. Cross road From the junction of two streets that are perpendicular to each other, two cyclists (each on another street) walked out. One ran 18 km/h and the second 24 km/h. How are they away from a) 6 minutes, b) 15 minutes?
19. Inlet minus outlet Water flows into the tank through two pipes and flows out of the third pipe spontaneously. The pipe A itself would fill the tank in 3 hours, the pipe B itself would fille in 4 hours, and the pipe C itself would flow out in 12 hours. How long will the tank.
20. Electric input power Solve problems related to electric power: a) U = 120 V, I = 0.5 A, P =? b) P = 200 W, U = 230 V, I =? c) I = 5 A, P = 2200W, U =?

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