Examples for 8th grade - page 12
- Strange x
For what x is true ??
- 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.
- Brothers and sisters
Lenka has as many brothers as sisters. Her brothers have twice as many sisters as brothers. How many brothers and sisters are in the family?
The cube weighs 18 kg. How weight is cube of the same material, if its dimensions are 3-times smaller?
- 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.
Calculate area of trapezoid ABCD with sides |AD|= 33 cm, |DC|=15 cm, |CB|=19 cm, |AB|=13 cm..
- 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?
- Apples and pears
Mom divided 24 apples and 15 pears to children. Each child received the same number of apples and pears - same number as his siblings. How many apples (j=?) and pears (h=?) received each child?
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?
- 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?
Coffee from the machine in the cup cost 25 cents. Coffee is 20 cents more expensive than the cup. How much is the cup?
In how many ways can be placed 6 athletes on the podium at the Olympics? Depend on the color of the metal.
- Sales off
If a sweater sells for $ 12 after a 25% markdown, what was its original price?
Practitioners lined up in rectangle with row with four, five or six exercisers, one always missing to full rectangle. How many exercisers were on the field, if they have estimated not been more than 100?
Calculate the perimeter and area of rhombus whose diagonals are 15 cm and 27 cm long.
- Mr. Vojta
Mr. Vojta put in the bank 35000 Kč.After a year bank him credited with interest rate of 2% of the deposit amount. How then will Mr. Vojta in the bank?
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?
- 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?
How many we must have at least nuts if we can equally divide it to 10 children, 14 children or 19 children and any nut left?