# Examples for 8th grade - page 50

1. Freight train
The train carries 525 tons of limestone in 29 wagons. Wagons are 15 tonne and 20 tons. How many is 15 ton and how many is 20 ton wagons?
2. Chocholate pyramid
How many chocolates are in the third shelf when at the 8th shelf are 41 chocolates in any other shelf is 7 chocolates more the previous shelf.
3. Three siblings
Three siblings have birthday in one day-today. Together they have 35 years today. The youngest is three years younger than middle and the oldest is 5 years older than middle. How old is each?
4. Jane and Miro
Jane brother Miro is 42 years. And he is three times old as it was Jane when Miro was for so many years as there are now Jane. How old is Jane?
5. Sprinter
Sprinter runs the relay 4 x 400 m to the handover at speed 42 km/h. A second runner is at the start of the handover area 20 m long and runs when it is the first sprinter at distance 10 m. Calculate the speed at which the second runner must run in order to.
6. Disease
Farmers'cooperative had a supply of feed for 50 cows to 6 days. Cows got insidious disease after 4 days, 10 of them died. How many total days that farmers had feed for cows?
7. Rectangle - sides 3
If in the rectangle ABCD we enlarge the side a by 5 cm and decrease the side b by 2 cm, the rectangle area will be reduced by 5 cm². When we decrease the length of the side a by 4 cm and and at the same time we increase the length of side b by 3 cm we incr
8. Crown coins
Jana saves two-crown and five-crown coins. She has ten coins in the cashier. How many two crowns and how many five crowns shw have if she saved 29 crowns?
9. Hřiště
Map scale is 1: 5000. The playground is rectangular and on the map has dimensions 10 cm and 5 cm What is area of playground in square meters in reality?
10. Fifth of the number
The fifth of the number is by 24 less than that number. What is the number?
11. Cube from sphere
What largest surface area (in cm2) can have a cube that was cut out of a sphere with radius 43 cm?
12. Sportsman
A trained athlete is able to exhale after a deep breath still 500 ml of air. At normal inhalation and exhalation is breathing 500 ml of air. Within one minute, one breath and exhaled 14 times. What part of breathing air per day is one exhalation?
13. Rotating cone
Calculate the volume and the surface area of a rotating cone of base radius r = 2.3 dm and a height h = 46 mm.
14. Two numbers
Find two numbers whose difference and ratio is 2.
15. Engine pulley
The engine has a 1460 rev / min (RPM). Disc diameter is 350 mm. What will be the disc peripheral speed in RPM? Pulleys on the engine has diameter 80mm, on a disc has diameter 160mm.
16. The pot
Diameter of the pot 38 cm. The height is 30 cm. How many liters of water can fit in the pot?
17. Passenger car and truck
From Kutna Hora left at 11:00 clock a truck at 60 km/h. At 12:30 behind him started passenger car at average speed 80 km/h. At what time and how far from Kutna Hora overtake a passenger car truck?