Examples for 8th grade - page 51
- Two trains meet
From A started at 7:15 express train at speed 85 km/h to B. From B started passenger train at 8:30 in the direction to A and at speed 55 km/h. The distance A and B is 386 1/4 km. At what time and at what distance from B the two trains meet?
- Center of gravity
In the isosceles triangle ABC is the ratio of the lengths of AB and the height to AB 10:12. The arm has a length of 26 cm. If the center of gravity T of triangle ABC find area of triangle ABT.
- The city
In the city is 2/4 of women married to 3/4 men. What percentage of townspeople is single (not married)?
- 10 pieces
How to divide the circle into 10 parts (geometrically)?
- Equilateral triangle v2
Equilateral triangle has a perimeter 36 dm. What is its area?
- Football season
Throughout the football season gave Adam the 23 goals more than Brano and 16 goals less than Karol. Edo gave the 6 goals more Dušan. Karol gave 5 more than Edo. Brano and Edo gave together 17 goals. How many goals gave each boy and how many goals gave the.
Blade circular saw with a diameter 42 cm turns 825 times per minute. Expresses his cutting speed in meters per minute.
When Peter threw stone in a box of water he discovered that the water level has risen by 8 cm. The box has a cuboid shape, the bottom has dimensions of 24 cm and 14 cm, height is 48 cm. What volume has a stone?
- Cube from sphere
What largest surface area (in cm2) can have a cube that was cut out of a sphere with radius 22 cm?
The first Earth satellite was flying at speed 8000 m/s. At that rate he circled the earth in 82 minutes. Jet flies at an average speed 800 km/h. How long would it take circle the earth round?
- Strange x
For what x is true ??
Express the expression ? as the n-th power of the base 7.
- Oil tank and pipes
The underground oil tank can be filled by two oil pipelines. The first is filled in 72 hours and the second in 48 hours. How many hours from the moment when first pipeline began to fill the oil is it necessary to start filling it with the second to fill in
- Grandmother's clocks
Grandmother's clock is late every hour by half a minute. Grandmother it by set exactly at 8.00 am. How many hours will show after 24 hours.?
Parachutists during freefall firstly held in groups of 4, then of 6, then 9, 12 and finally of 18 members. How many parachutists jump at least should be, if at each group must all be involved.
You're the owner of the transport 's learning playground. Buy bicycles of two colors but you've got to spend accurately 120000 Kč. Blue bike costs 3600Kč and red bicycle 3200Kč.
- Circle and hexagon
Calculate the radius of a circle whose circumference is 6.8 cm longer than the circumference of the inscribed regular hexagon.
- Mother and daughter 2
The mother is 40 years older than her daughter. How old is the mother if her age is eight thirds age of daughter?
- 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.
What is the inside diameter of the cylinder container and if half a liter of water reaches a height 15 cm?