Geometry begins with the simplest ideas: points, lines, and planes. A point marks an exact location (like a dot on paper). A line is a straight path that goes on forever in both directions. A plane is a flat surface that extends infinitely. Which statement correctly describes a line?

Lines can be "cut" into smaller parts. A line segment is part of a line with two endpoints – it has a definite beginning and end. A ray has one endpoint and extends infinitely in one direction (like a laser beam from a source). If you have a starting point A and the line goes through point B forever beyond, what geometric figure is this?

An angle is formed when two rays share a common endpoint. That common endpoint is called the vertex. The two rays are called the sides of the angle. Angles are measured in degrees (°), from 0° to 360° around a circle. When you open a door, you are creating an angle between the door and the door frame! In angle ABC (written ∠ABC), which point is the vertex?

Angles are classified by their degree measure. An acute angle measures less than 90° (sharp, like the tip of a slice of pizza). A right angle measures exactly 90° (perfect corner of a square or book). An obtuse angle measures between 90° and 180° (wide, like a reclining chair). A straight angle measures exactly 180° (a straight line). If an angle measures 145°, what type of angle is it?

Perimeter is the distance AROUND a shape. Think of it as the length of fence needed to enclose a garden. For a polygon (a closed shape with straight sides), you simply add up all the side lengths. A rectangle has length 12 meters and width 5 meters. What is its perimeter?

Area measures the space INSIDE a shape. While perimeter is like fence length, area is like the amount of grass seed needed to cover the garden. For a rectangle, area = length × width. The answer is in square units (like m², ft², in²). A rectangular classroom measures 15 feet by 20 feet. What is the floor area?

Every triangle has three angles that always add up to 180°. This is one of the most important rules in geometry! It works for EVERY triangle – big or small, any shape. If a triangle has angles of 45° and 55°, what is the measure of the third angle?

Triangles can be classified by their side lengths. An equilateral triangle has all three sides equal (and all three angles equal – each 60°). An isosceles triangle has at least two equal sides (and the angles opposite those sides are equal). A scalene triangle has NO equal sides (all sides different lengths). If a triangle has side lengths 5 cm, 5 cm, and 8 cm, what type of triangle is it?

The Pythagorean Theorem is a famous formula for right triangles. It states: a² + b² = c², where a and b are the legs (the sides that form the right angle), and c is the hypotenuse (the longest side, opposite the right angle). For a right triangle with legs of 3 inches and 4 inches, what is the length of the hypotenuse?

Volume measures the space INSIDE a 3D shape. While area is for flat shapes, volume is for solid objects – it tells you how much a box can hold. For a rectangular prism (like a shoebox), volume = length × width × height. The answer is in cubic units (like cm³, m³, ft³). A fish tank has length 40 cm, width 20 cm, and height 30 cm. How many cubic centimeters of water can it hold?