# Examples for 9th grade - page 112

1. Pebble The aquarium with internal dimensions of the bottom 40 cm × 35 cm and a height of 30 cm is filled with two-thirds of water. Calculate how many millimeters the water level in the aquarium rises by dipping a pebble-shaped sphere with a diameter of 18 cm. There are 15 boys and 12 girls at the graduation party. Determine how many four couples can be selected.
3. Drive to NJ Ed drove to New Jersey at 30mph. He drove back home in 3 hours at 50 mph. How many hours did it take Ed to drive to New Jersey?
4. Working alone Tom and Chandri are doing household chores. Chandri can do the work twice as fast as Tom. If they work together, they can finish the work in 5 hours. How long does it take Tom working alone to do the same work?
5. Tree trunk What is the smallest diameter of a tree trunk that we can cut a square-section square with a side length of 20 cm?
6. Base of prism The base of the perpendicular prism is a rectangular triangle whose legs length are at a 3: 4 ratio. The height of the prism is 2cm smaller than the larger base leg. Determine the volume of the prism if its surface is 468 cm2.
7. Three pumps together One pump fills the tank in 1.5 hours, the second in 2 hours, and the third in 3 hours 20 minutes. How many minutes will the tank fill with three pumps if they work simultaneously?
8. The second The second angle of a triangle is the same size as the first angle. The third angle is 12 degrees larger than the first angle. How large are the angles?
9. Prices The price of the product was increased by 35%. How many percents of the new price we have to make it cheaper so that its price is equal to the original price?
10. Set of coordinates Consider the following ordered pairs that represent a relation. {(–4, –7), (0, 6), (5, –3), (5, 2)} What can be concluded of the domain and range for this relation?
11. Pine's forest There were so many pines in the forest that if they were sequentially numbered 1, 2, 3,. .. , would use three times more digits than the pine trees alone. How many pine trees were there in the forest?
12. Two water containers In the first container, there are 200 m3 of water and in the second 40 m3. The first container will flow down at a rate of 10 m3 water per hour. At the same time flows to the second rate of 5 m3 per hour. After how many hours there will be three times less
13. Two math problems 1) The sum of twice a number and -6 is nine more than the opposite of that number. Find the number. 2) A collection of 27 coins, all nickels, and dimes, is worth \$2.10. How many of each coin are there? The dime, in United States usage, is a ten-cent coin
14. Equation with mixed fractions 2 3/5 of 1430+? = 1900. How to do this problem
15. Two rectangles 2 A square of area 36 cm2 is cut out to make two rectangles. A and B The area of area A to area B is 2 : 1 Find the dimensions of rectangles A and B.
16. Geometric progressiob If the sum of four consective terms of geometric progression is 80 and arithmetic mean of second and fourth term is 30 then find terms?
17. Time passing 6 years ago, Marcela's mother was two times older than her and two times younger than her father. When Marcela is 36, she will be twice as young as her father. How old are Marcela, her father, and mother now?
18. Copper sulphate How much g of water do we have to add to 240 g of an 84% CuSO4 solution to produce a 60% solution? (Express the mass of crystalline CuSO4 in the original solution and in the resulting solution and compare them. )
19. Drilling machine A manufacturing firm purchased a heavy duty drilling machine. They were given two payment options: Option 1: Make a payment of \$46,000 immediately to settle the invoice for the machine. Option 2: Make a payment of \$21,500 immediately and the balance of \$

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