# Examples for 8th grade - page 55

- Number

What number is 20 % smaller than the number 198? - Efficiency

A certain device consumes 28 kW and delivers 14 kW. Find its efficiency. - The ship

The ship went upstream speed of 20 km/h in relation to water. River flows at speed 10 km/h. After half an hour, he stopped and returned downstream to the starting point. How long it took way back when even if downstream speed of ship is 20 km/h in relation - Pool

Pool is filled with two water supply. The first supply fill pool for nine hours, the second for six hours. How many hours will take fill the pool when the water flows in through the first supply 3 hours and then we will open a second supply? - Isosceles trapezoid

What is the height of an isosceles trapezoid, the base of which has a length of 11 cm and 8 cm and whose legs measure 2.5 cm? - Stamps and albums

Michail has in three albums stored 170 stamps. In the first album, there are 14 more than in the second and in the second is by 1/5 less than in the third. How many stamps are in the first album? - Reduce of the volume

Calculate how many % reduce the volume of the cube is we reduced length of each edge by 10%. - Bob and Bobek

At 10h 20min runs Bobek from hat at average speed 12 km/h. At what time must run out Bob at speed 18 km/h to catch him 9 kilometers from the hat? - Boots

Master shoemaker has three apprentices. First do one pair of boots for two days, second for 1 day, third on 1.5 day. If they worked together, for how long it would take made a couple of boots? - Double-track

On double-track express met with a freight train. Express travel at speed 72 km/h, a freight train at speed 36 km/h. After what time period will be from 9 km apart? - Football season

Throughout the football season gave Adam the 23 goals more than Brano and 16 goals less than Karol. Edo gave the 6 goals more Dušan. Karol gave 5 more than Edo. Brano and Edo gave together 17 goals. How many goals gave each boy and how many goals gave the. - High wall

I have a wall 2m high. I need a 15 degree angle (upward) to second wall 4 meters away. How high must the second wall? - CD disc

A compact disc has a diameter of 11.8 cm. What is the surface area of the disc in square centimeters? - President

The country has 5.11 million citizens which 2.12 million are voters. Turnout was 34.4%. President R. F. was elected from 20 candidates for president and won with 38% of votes. Calculate what percentage of the country's citizens voted R.F. as president o - Concrete box

The concrete box with walls thick 5 cm has the following external dimensions: length 1.4 m, width 38 cm and height 42 cm. How many liters of soil can fit if I fill it to the brim? - Fraction

For what x expression ? equals zero? - Chord 4

I need to calculate the circumference of a circle, I know the chord length c=22 cm and the distance from the center d=29 cm chord to the circle. - Tiles

How much you will pay CZK for laying tiles in a square room with a diagonal of 8 m if 1 m^{2}cost CZK 420? - Gold coin

Gold coin contains 964 promile pure gold, which is 7.16 g. What is the weight of coin in grams? - Box of chocolates

In a box of chocolates was 16 candies. Christopher and Luke they were distributed: a) Christopher had about 4 candies over Luke, b) Christopher had about 6 candies less than Luke, c) Christopher had 3 times more sweet than Luke. How many had each boy can

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