# Examples for 8th grade - page 31

1. Divisors
Find all divisors of number 493. How many are them?
2. Circle sector
Circular sector with a central angle 80 ° has area 1257 cm2. Calculate its radius r.
3. RT and ratio
A right triangle whose legs are in a ratio 6:12 has hypotenuse 68 m long. How long are its legs?
4. Cars plates
How many different licence plates can country have, given that they use 3 letters followed by 3 digits?
5. Four-digit number
Find also a four-digit number, which quadrupled written backwards is the same number.
6. Field with vegetables
Field planted with vegetables has shape of a rectangular isosceles triangle with leg length of 24 m. At the vertices of the triangle are positioned rotating sprinklers with a range of 12 m. How much of the field sprinkler doesn't irrigated?
7. Workman - shift
The worker produces 300 components per shift. How many components would be produced in 18 shift, if his performance gradually increased every shift by 3 components?
8. Cube 6
Volume of the cube is 216 cm3, calculate its surface area.
9. Swing
A child weighing 12 kg is sitting on a swing at a distance of 130 cm from the axis of rotation. How far away from the axis of rotation (center) must sit down his mother weighs 57 kg if she wants to be swing in balance?
10. Trapezoid ABCD
Calculate the perimeter of trapezoid ABCD if we know the side c=15, b=19 which is also a height and side d=20.
11. Map 2
At what scale is made map if the distance 8.2 km corresponds on the map segment 5 cm long?
12. Water
On the lawn which has area 914 m2 rained 3 mm of water. How many liters of water rained?
13. The body
The body on the figure consists of cubes with an edge length 10 cm. What surface has this body?
14. Number
Is number 5.146852 irrational?
15. Building base
Excavation for the building base is 350x600x26000. Calculate its volume in m3.
16. Revenue
Mr. Robert and Mr. Norbert get together € 1400. The revenue split in the ratio of 4:3, depending upon each work. How many got each of them?
17. Tunnels
Mice had built an underground house consisting of chambers and tunnels: • each tunnel leading from the chamber to the chamber (none is blind) • from each chamber lead just three tunnels into three distinct chambers, • from each chamber mice can get to any
18. Spirit
From 55% and 80% spirit we would like to produce 0.2 kg of 60% spirit. How many of them we must use in a solution?