πr²Circles and triangles: math practice, grade 9

Practise “Circles and triangles” online for free. Five right answers in a row make the tasks harder, two mistakes in a row make them easier. Right answers earn coins for games.

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Example problems

These are only examples: the practice makes new tasks every time.

1. A circle’s diameter is 10 cm. Find its circumference.

   C = ?π

   Answer

   10

2. A circle’s diameter is 18 cm. Find its area.

   S = ?π

   Answer

   81

3. The radius is 12 cm and the sector’s angle is 120°. Find the area of the sector.

   S = ?π

   Answer

   48

4. The radius is 6 cm and the arc’s angle is 240°. Find the length of the arc.

   l = ?π

   Answer

   8

5. Find the area of the triangle.

   S = ?

   Answer

   24

6. Find the third side of the triangle.

   c = ?

   Answer

   7

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