# Examples for 9th grade

- The surface area

How much percent will the surface area of a 4x5x8 cm block increase if the length of the shortest edge is increased by 2 cm? - Cuboid and ratio

Find the dimensions of a cuboid having a volume of 810 cm^{3}if the lengths of its edges coming from the same vertex are in ratio 2: 3: 5 - Squares ratio

The first square has a side length of a = 6 cm. The second square has a circumference of 6 dm. Calculate the proportions of the perimeters and the proportions of the contents of these squares? (Write the ratio in the basic form). (Perimeter = 4 * a, conte - Five-gon

Calculate the side a, the circumference and the area of the regular 5-angle if Rop = 6cm. - Fall sum or same

Find the probability that if you roll two dice, it will fall the sum of 10, or the same number will fall on both dice. - Annulus

Two concentric circles with radii 1 and 9 surround the annular circle. This ring is inscribed with n circles that do not overlap. Determine the highest possible value of n. - Tourist cottage

The tourist cottage has 11 rooms for 16 guests, some of them are doubles, some singles. How many are double rooms and how many are single rooms? - Two gardens

The total area of the two gardens is 864 m^{2}. The first garden is 60 m^{2}smaller than three times the second garden. What is the area of each garden? - Twelve ties

The price of 12 ties before the discount was the same as 15 ties after discount. Calculate the price of 1 tie after discount, if you know that the discount price of one tie fell by 40 CZK? - Corona virus

Calculate an estimate of the percentage of GDP (Gross Domestic Product) declined due to the quarantine related to the corona COVID-19 virus that lasts for 2 months, during which time the economic activity is down by 80%. - Wall thickness

The hollow metal ball has an outside diameter of 40 cm. Determine the wall thickness if the weight is 25 kg and the metal density is 8.45 g/cm^{3}. - What percentage

What percentage of the Earth’s surface is seen by an astronaut from a height of h = 350 km. Take the Earth as a sphere with the radius R = 6370 km - What percent

What percent of 51 3/5 is 47 2/5? - Self-oscillation period

The water in the vessel carried by the boy has a self-oscillation period of 0.8 s. What is the size of the boy's movement speed when the length of the boy's step is 60 cm? Give the result in m/s. - Discounts 2

The local fitness center offers membership discounts for hospital employees. According to the membership brochure, you will receive a discount of 25% on a membership that normally costs $65 per month. How much will you pay for an annual membership if you - Runners

If John has a running speed of 3.5miles per hour and Lucy has a speed of 5 miles per hour. If John starts running at 10:00 am and Lucy starts running at 10:30 am, at what time will they meet? (as soon as possible) - Birth

Let's assume that the probability of the birth of a boy and a girl in the family is the same. What is the probability that in a family with five children, the youngest and oldest child is a boy? - Adding

Divide number 135 into two additions so that one adds 30 more than 2/5 of the other add. Write the bigger one. - Volume of wood

Every year, at the same time, an increase in the volume of wood in the forest is measured. The increase is regularly p% compared to the previous year. If in 10 years the volume of wood has increased by 10%, what is the number p? - Power line pole

From point A, the power line pole is seen at an angle of 18 degrees. From point B to which we get when going from point A 30m away from the column at an angle of 10 degrees. Find the height of the power pole.

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