Similar shapes may or may not be congruent
The length of DE is 42 units
The given parameters are:
[tex]\mathbf{AC = 84}[/tex]
[tex]\mathbf{BA = 2BD}[/tex] --- Because DE is at the midpoint
The equivalent ratio is then represented as:
[tex]\mathbf{BD : DE = BA : AC}[/tex]
Substitute [tex]\mathbf{BA = 2BD}[/tex]
[tex]\mathbf{BD : DE = 2BD : AC}[/tex]
Express as fraction
[tex]\mathbf{\frac{DE}{BD }= \frac{AC}{2BD }}[/tex]
Make DE the subject
[tex]\mathbf{DE= \frac{AC}{2BD } \times BD}[/tex]
[tex]\mathbf{DE= \frac{AC}{2 }}[/tex]
Substitute 84 for AC
[tex]\mathbf{DE= \frac{84}{2 }}[/tex]
[tex]\mathbf{DE= 42}[/tex]
Hence, the length of DE is 42 units
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