Geometry for grade 5.

Points:

A point is like a dot. We join dots to make different shapes. Each point is given a name.

   . A

                        . B

A & B are two points.

 

Line Segment:

Two points join together to make a line. This line is named by the name of its point. If we have made a line by joining point A and B then we call this line AB.

 

Ray:

A ray is like a line but it can be extended from one of its end having the arrow head.

                                               

The above ray can be extended from its end called B.

 

Line:

A line has arrows on both of its sides and thus it can be extended towards both sides.

 

                                                               

Angles:

When two rays have a common end point they form an angle. Their common end point is called vertex and the rays are called arms of the angle. Among these arms one is called the initial ray and the other is called the terminal ray. The vertex is always in the middle of the two arm of the angle.

This angle has to be named. This name is usually three lettered or one lettered. One letter to refer the vertex, one letter to refer one end point of the ray and one letter to refer the second end point of the other ray.

 

In the above angle diagram A is terminal ray, B is initial ray and O is the vertex. We can also refer to an angle by just its vertex name. So we can call the angle O or AOB.

 

Closed figures:

The figures in which if we start from one point we reach the same point.

Closed figures are,

 

1. Non simple closed figures:

If we across a point more than twice , in a figure than the figure is known as non simple closed figure.

 

2. Simple closed figures:

If in any figure no point is repeated then it is called simple closed figure.

 

Types of simple closed figures:

Following are few shapes which are example of  simple closed figures,

 

a)      Triangle.

              

b)            Rectangle.

 

 

c)      Square.

 

      

d)      Parallelogram.

 

e)      Rhombus.

 

f)       Circle.

                 

 Perimeter:

Perimeter is the sum of lengths of sides of any closed shape.

 

1. Perimeter of a triangle:

Perimeter of a triangle is sum of it sides.

Example:

If we have a triangle having side length 4cm ,3.5cm &2.8cm .Then;

perimeter = 4 + 3.5 + 2.8 = 10.3cm

 

 

2. Perimeter of rectangle:

The perimeter of rectangle is 2 × (l + w),where l is the length of the rectangle and  b is the width.

Example:

If length of a rectangle = 4.3cm and its width is 3.8cm, then its perimeter is 16.2cm.

 

3. Perimeter of square:

The perimeter of a square if four times length of its side.

Example:

If a square has side length 3cm then its perimeter is 4(3) = 12cm.

 

4. Perimeter of a parallelogram:

It is sum of adjacent sides multiplied by 2.

If a parallelogram has two of its side (adjacent side) of 3cm and the other two of 2cm then the perimeter will be 3 ×2 = 6cm.

 

5. Perimeter of a rhombus:

It is sum of the sides or 4 multiplied by side length.

The perimeter of a rhombus of side length 5cm will be 4(5) = 20 cm.

 

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