Examples for 8th grade - page 31
24-member group of divers carries the air for 11 hours of diving. 4 members of the expedition sick or wasn't came. How many hours is sufficient air to other divers?
- Volume and surface
Calculate the volume and surface area of the cylinder when the cylinder height and base diameter is in a ratio of 3:4 and the area of the cylinder jacket is 24 dm2.
- Train from Brno
First train started from Brno at 8 am at 60 km per hour. Second train started from Opava at 7 o'clock at the speed of 40 kilometers per hour. In how many hours and how far from cities trains meet when the distance of cities is 200 kilometers.
- Gon functions
Decide which of the numbers (values of trigonometric functions) are positive and which are negative (or zero). Positive mark +1 and negative -1.
7.4 meters long ladder is leaning against the wall of the well and its lower end is 1.1 meters from this wall. How high from the bottom of a well is the top edge of the ladder?
- Area 4gon
Calculate area of 4-gon, two and the two sides are equal and parallel with lengths 7, 15, 7 and 15. Inner angles are 45°, 135°,45°, 135°.
- Again saw
From the trunk of the tree we have to a sculpture beam with rectangular cross-section with dimensions 128 mm and 140 mm. What is the trunk smallest diameter?
800 pennies have the same value as 100 ducats. 100 pennies have the same value as 250 tolars. How many ducats has the same value as 100 tolars?
For every 5 minutes writes Dana 10 invitations, while Anna 14 invitations. How long will write together 120 invitations?
- Rising price
The book first become more expensive by 5 euros. New price was later increased by 13%. After the second price increase book cost 47 euros. What was the original price of the book?
- Cube 6
Volume of the cube is 216 cm3, calculate its surface area.
- Compare II
Which of the numbers 158, 815 is greater?
- Four-digit number
Find also a four-digit number, which quadrupled written backwards is the same number.
- Katy MO
Kate draw triangle ABC. Middle of AB have mark as X and the center of the side AC as Y. On the side BC wants to find the point Z such that the content area of a 4gon AXZY was greatest. What part of the triangle ABC can maximally occupy 4-gon AXZY?
The children were on a school trip to the mountain . One third of the journey went by the train and continue by bus. When you get off the bus, they remained a third of the distance they traveled by bus. What part of journey children went by the bus (wrote
Area of trapezoid is 135 cm2. Sides a, c and height h are in a ratio 6:4:3. How long are a,c and h? Make calculation...
- Two workers
Two workers carry will do certain work for 12 days. After 8 days of working was one removed, and then the other finished the job alone in 10 days. For how many days would do this work alone each worker?
- Swimming pool 4
The pool shaped cuboid measuring 12.5 m × 640 cm at the bottom is 960hl water. To what height in meters reaches the water level?
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
- Mushrooms from the forest
Magda and Tereza goes to pick mushrooms. Total found 70 mushrooms. Magda found that between fungi found 5/9 bedel. Tereza discovered that she found among fungi are 2/17 champignons. How many mushrooms found Magda?