# Examples for 8th grade - page 28

- Carpenter

From wooden block carpenter cut off a small cuboid block with half the edge length. How many percent of wood he cut off? - Reciprocal

What is the reciprocal of the sum of the reciprocals of 7 and 2? - Horizontal Cylindrical Segment

How much fuel is in the tank of horizontal cylindrical segment with a length 10m, width of level 1 meter and level is 0.2 meters below the upper side of the tank? - Car

The driver of a car is to get to 378 km distant city. From atlas found that 99 km will have to pass through the cities at average speed 48 km/h. Remainder of the journey pass outside the cities at average speed 117 km/h. Calculate how many hours it will ta - Strawberries

Father collects strawberries himself in 4 hours, son in 10 hours. How long will it take them along when dad comes to help son collect strawberries after 4 hours? - Equilateral cylinder

Equilateral cylinder (height = base diameter; h = 2r) has a volume of V = 221 cm^{3}. Calculate the surface area of the cylinder. - Racer

The first racer run at a speed 12 m/s and is 470 meters before the finish and ahead 22 meters before second competitor. At what speed must run the second racer to catch first racer at the finish line? - Chess

How many ways can select 3 fields on classic chess board with 64 fields, so that fields don't has the same color? - Cars plates

How many different licence plates can country have, given that they use 3 letters followed by 4 digits? - Apartments

Apartment on the first floor was 10% more expensive than the same apartment on the second floor. The difference was 105 Kc annually. Calculate the annual rent of the apartment in the first floor and from apartment on the second floor. - Paper box

Calculate the consumption of paper on the box-shaped quadrangular prism with rhombic footstall, base edge a=6 cm and the adjacent base edges forms an angle alpha = 60 °. Box height is 10 cm. How many m^{2}of the paper consumed 100 such boxes? - Base

Compute base of an isosceles triangle, with the arm a=9 cm and a height above the base h=6 cm. - Bath

In the bath is 30 liters of hot water. Then added 38 liters of cold water at temperature of 17 °C decreased temperature of water to 48 °C. What was the initial temperature of the hot water? - 30-60-90

The longer leg of a 30°-60°-90° triangle measures 7. What is the length of the shorter leg? - Trapezoid ABCD

Calculate the perimeter of trapezoid ABCD if we know the side c=25, b=16 which is also a height and side d=27. - Around the flowerbed

Around a rectangular flowerbed with dimensions 5.25 m and 12.5 m are to be planted roses equally spaced so that the roses found in every corner of the flowerbed and consumed them as little as possible. a) At what distance are planted roses? b) How many ro - Hockey players

After we cycle five hockey players sit down. What is the probability that the two best scorers of this crew will sit next to each other? - Racing track

On the racing track circling three cars. The first passes one circuit for 8 seconds, the second for 16 seconds and a third for 15 seconds. a) Calculate number of seconds since the start to catch all three cars together for the first time again across the. - Two cars

From the town A to town B started two cars. The first at 7:00 at average speed 60 km per hour, the second at 10:00 at average speed 100 km per hour. The first car will not stay in B, and on the way back meet the second car at half way from A to B. At what. - Grandson and granddad

Grandson with grandpa they counted how many years have together. Their product is 365. How many years is the sum of their years.

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