Examples for 8th grade - page 29
- Water pool
What water level is in the pool shaped cuboid with bottom dimensions of 25 m and 10 meters, when is 3750hl water in the pool.
- Painting school
Redecoration school had scheduled for four crew to 10 days. After two days a single worker ill. For how many days the school was painted when remain workers working with the same tempo?
Wood contains 12% water. 1 m3 of wood weighs 650 kg. How many liters of water it contains?
- Lenka and money
When Lenka bought pants from 1/3 of her savings shirt from 1/5 and 1/8 spent at the hairdresser, she is left 328 Kč. How much money was saved? How much hairdresser cost?
- 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?
Sisters Zuzka Lenka and Vierka has save for a new bike. Zuzka save € 90, Lenka save € 90 and Vierka save € 82. Missing 30% gave them their mother. What is the price of the bike?
Area of circle inscribed in a square is 6. What is the area of a circle circumscribed around a square?
From the cottage started first group of tourists at 10:00 AM at speed 4 km/h. The second started after them 39 minutes later at speed 6 km/h. How long and how many kilometers from the cottage will catch the first group?
- Mother and daughter
Three years ago mother was three times older than daughter. After nine years she will be only twice old. How old is mother (and daughter)?
- Task of the year
Determine the number of integers from 1 to 106 with ending four digits 2001.
The top of a lighthouse is 12 m above the sea. How far away is an object which is just “on the horizon”? [Assume the earth is a sphere of radius 6378.1 km.]
Three metal balls with volumes V1=41 cm3 V2=58 cm3 and V3=83 cm3 melted into one ball. Determine it's surface area.
Ping pong balls have a diameter of approximately 3 cm. They are sold in boxes of 3 pieces: each box has the shape of a cuboid with a square base. The balls touch the walls of the box. Calculate what portion of the internal volume of the box is filled wit
Mr. Johnson's had monthly salary 966 USD since the beginning of year. From which month his salary was increased by 74 USD, when in year earned 11814 USD (enter as a number from 1 to 12)?
- Lead cube
Calculate the edge of the cube made from lead, which weighs 11 kg. The density of lead is 11341 kg/m3.
- Rectangle - sides ratio
Calculate area of rectangle whose sides are in ratio 1:7 and perimeter is 735.
- Two numbers
Find two numbers whose difference and ratio is 10.
- Washing mashine
Family buy a washing machine for 350e. Cash paid 280e. What percentage of the total price must still pay the washer?
- Water reservoir
The water reservoir is filled with one pump for 4 days by the second one for 9 days. Outlet can drain tank in 12 days. How long take fill the reservoir if both pumps are running and not closed outlet channel.
- Disinfecting solution
How much distilled water is necessary to pour into 500 ml of 33% hydrogen peroxide solution to obtain 3% disinfecting solution?