# Examples for 8th grade - page 15

- Expressions

Expression (3a-7).(3a+7) is identical with: ? - Reciprocal

What is the reciprocal of the sum of the reciprocals of 7 and 2? - VAT

John paid 1000 Euros in store for purchase. Calculate value added tax (VAT), which paid in purchase, if the VAT rate is 20%. - Circumference - a simple

What is the ratio of the circumference of any circle and its diameter? Write the result as a real number rounded to 2 decimal places. - Two pumps

The first pump fills the tank in 24 hours second pump in another 40 hours. For how long will take fill the tank if operate both pumps at the same time? - Pyramid Z8–I–6

Each brick of pyramid contains one number. Whenever possible, the number in each brick is lowest common multiple of two numbers of bricks lying directly above it. That number may be in the lowest brick? Determine all possibilities. - Water

On the lawn which has area 243 m^{2}rained 5 mm of water. How many liters of water rained? - Gold coin

Gold coin contains 963 promile pure gold, which is 8.39 g. What is the weight of coin in grams? - Washing machine

The price of washing machine was decreased by 24% and then by 59 € due small sales. After two price decreases cost € 300. How much was originally cost? - Bits, bytes

Calculate how many different numbers can be encoded in 16-bit binary word? - A family

A family of four pays for garbage collection per year 1800 Kč. How many crowns a year the waste company get from the house where lives 93 people? - Scouts

The boys from scout group traveled 3 days distance 105 km. Every day walked 1.3 km less than the previous day. How many kilometers scouts walked in the first day? - Similarity

Rectangle ABCD has dimensions of 9 cm and 6 cm. Rectangle PQRS has dimensions 7 cm and 8 cm. Determine coefficient of the similarity k of the rectangles, if they aren't similar enter zero as the coefficient of similarity. - Newton's task

Grass grows in the meadow equally fast and evenly. It is known that 58 cows graze meadow for 30 days and 80 cows by 19 days. How many cows graze meadow for 6 days? - Hole

In the center of the cube with edge 15 cm we will drill cylinder shape hole. Volume of the hole must be 28% of the cube. What drill diameter should be chosen? - Volleyball

8 girls wants to play volleyball against boys. On the field at one time can be six players per team. How many initial teams of this girls may trainer to choose? - Class 8.A

Three quarters of class 8.A went skiing. Of those who remained at home one third was ill and the remaining six were on math olympic. How many students have class 8.A? - Jan

Jan is 13 years and Peter 21 years old. For how many years will their ages in the ratio of 7:9? - 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? - Simple interest

Peter put into bank 1028 euros deposit. After 6 years on account overall was 1242 euro. What was the interest rate if bank add simple interest?

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