Question

The height of a triangle is half the length of its base. The area of the triangle is 12.25cm. Find the height

Answer 1

Answer:  The height of the triangle is:  " 3.5 cm " .
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Note:  The formula/equation for the area, "A" , of a triangle is:

           A = (1/2) * b * h  ;  or write as:  A = (b * h) / 2 ; 
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 in which:   "A = area of the triangle" ; 
                  "b = base length" ; 
                  "h = "[perpendicular] height" ; 
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     Given:  h = (b/2) ;
                  A = 12.25 cm²
{Note:  Let us assume that the given area was "12.25 cm² " .}. 
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 We are to find the height, "h" ; 

The formula for the Area, "A", is:   A = (b * h) / 2 ; 

Let us rearrange the formula ;
 to isolate the "h" (height) on one side of the equation; 

→ Multiply EACH side of the equation by "2" ; to eliminate the "fraction" ; 

2*A = [ (b * h) / 2 ] * 2 ; 

   to get:   " 2A = b * h " ; 

↔    " b * h = 2A " ; 

Divide EACH SIDE of the equation by "b" ; to isolate "h" on one side of the equation: 

        →  (b * h) / b  = (2A) / b ; 

to get: 
  
        →   h  =  2A / b ; 

Since  "h = b/2" ; subtitute "b/2" for "h" ; 
 
Plug in:  "12.25 cm² " for "A" ;

       →  b/2  =  2A/b ;   →  Note:  " 2A/b = [2* (12.25 cm²) ] / b " ;

Note:  " 2* (12.25 cm²) = 24.5 cm² ; 

Rewrite as: 

       →  b/2  =  (24.5 cm²) / b ;
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Cross-multiply:   b*b = (24.5 cm²) *2 ; 

to get:   b² = 49 cm² ; 

Take the "positive square root" of each side of the equation" ; 
            to isolate "b" on one side of the equation ; & to solve for "b" ; 

             →  +√(b²)  =  +√(49 cm²) ; 

             →  b = 7 cm ; 

Now, we want to solve for "h" (the height) :
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             →  h = b / 2 = 7 cm / 2 = 3.5 cm ; 
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Answer:  The height of the triangle is:  " 3.5 cm " .
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