Examples for 8th grade - page 10
The cube weighs 18 kg. How weight is cube of the same material, if its dimensions are 3-times smaller?
Calculate area of trapezoid ABCD with sides |AD|= 33 cm, |DC|=15 cm, |CB|=19 cm, |AB|=13 cm..
Five painters painting the fence for eight days. How many days over will take work if paint the fence only four decorators?
- Strange x
For what x is true ??
The store got three kinds of tissues - 132 children, 156 women and 204 men. Tissues each species were packed into boxes after the number of pieces the same for all three types (and greatest). Determine the number, if you know that every box has more than 6
- Two doctors
Doctor A will determine the correct diagnosis with a probability 80% and doctor B with a probability 72%. Calculate probability of correct diagnosis if patient is diagnosed by both doctors.
Marie earns 1.8 liters of blueberries for 1.2 hours, Peter 2.6 liters for 1.2 hours. How long have earns together one liter?
On coins found was stated that from the year 87 BC. It is right?
Coffee from the machine in the cup cost 25 cents. Coffee is 20 cents more expensive than the cup. How much is the cup?
- The dice
What is the probability of events that if we throw a dice is rolled less than 6?
- The bridge
Across the circle lakepasses through its center bridge over the lake. At three different locations on the lake shore are three fishermen A, B, C. Which of fishermen see the bridge under the largest angle?
- Bus vs. train
Bus started from point A 25 minutes before the train started from the same place. The bus went an average speed of 41 km/h, train 67 km/h. To point B train and bus arrived simultaneously. Calculate time of train journey, if train and bus travelled the.
- Eiffel Tower
Eiffel Tower in Paris is 300 meters high, is made of steel. Its weight is 8000 tons. How tall is the tower model made of the same material, if it weigh is 4.8 kg?
- Volume from surface area
What is the volume of the cube whose surface area is 96 cm2?
The longer leg of a 30°-60°-90° triangle measures 7. What is the length of the shorter leg?
Siblings collect a 2-crowns and 5-crowns. Together have 80 coins with a total of value 310 crowns. How many saved two-crowns and how many five-crowns?
Area of square garden is 6/7 of triangle garden with sides 96 m, 60 m and 60 m. How many meters of fencing need to fence a square garden?
Calculate the perimeter and area of rhombus whose diagonals are 15 cm and 27 cm long.
- Motion problem
From Bratislavy to Martina go car at speed 83 km/h. From Martina to Bratislavy go another car at speed 62 km/h. How many minutes before the meeting will be cars 21 km away?
In how many ways can be placed 6 athletes on the podium at the Olympics? Depend on the color of the metal.