Mathematics
Grade9
Easy

Question

The area of a regular octagon is 695.3 square cm, and the sides are 12 cm. What is the length of the apothem?

  1. 17.2    
  2. 14.5    
  3. 13.9    
  4. 12.6    

hintHint:

Polygon is a two- dimensional closed figure which is made up of three or more line segments. Each polygon has its own properties based on the number of sides. Area of a regular polygon can be determined using the formula A r e a space o f space t h e space p o l y g o n equals 1 half cross times P e r i m e t e r space o f space t h e space p o l y g o n cross times A p o t h e m . Here, we have to find the apothem of the given polygon using the area formula.

The correct answer is: 14.5


    In the question it is given that,
    Area of a regular octagon= 695.3 square cm
    Length of each side= 12 cm
    Here, we have to find the length of the apothem.
    Perimeter of the polygon = Length of each side × No. of sides
    =12×8
    = 96
    Now,
    Area of the polygon = 1 half cross times P e r i m e t e r space o f space t h e space p o l y g o n cross times A p o t h e m
    695.3 =fraction numerator 1 over denominator 2 end fraction×96× Apothem
    =fraction numerator 695.3 cross times 2 over denominator 96 end fraction
    =14.5
    So, the length of the apothem of the polygon is 14.5.
    Therefore, the correct option is b, i.e., 14.5.

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