Since BC is parallel to DE, triangles ABC and ADE are similar. What are the lengths of the unknown sides?

A. AC = 14 cm; CE = 8 cm
B. AC = 12 cm; CE = 7 cm
C. AC = 5 cm; CE = 10 cm
D. AC = 10 cm; CE = 5 cm

Since BC is parallel to DE triangles ABC and ADE are similar What are the lengths of the unknown sides A AC 14 cm CE 8 cm B AC 12 cm CE 7 cm C AC 5 cm CE 10 cm class=

Respuesta :

Answer:

Option D. AC= 10 cm and CE= 5 cm

Step-by-step explanation:

From the given figure two triangles ΔABC and ΔADE are similar and two lines BC║DE.

From these similar triangles we know

[tex]\frac{AB}{AD}=\frac{BC}{DE}=\frac{AC}{AE}[/tex]

[tex]\frac{8}{12}=\frac{BC}{9}=\frac{AC}{AE}[/tex]

Therefore [tex]\frac{AC}{AE}=\frac{8}{12}=\frac{2}{3}[/tex]

Or AC=[tex]\frac{2}{3}AE[/tex]

Now from pythagoras theorem

AE = √(AD²+ED²) = √(12²+9²) = √(144+81) =√225 = 15 cm

Since we know side AC = [tex]\frac{2}{3}AE[/tex]

                                        = [tex]\frac{2}{3}\times 15[/tex]

                                        = 10 cm

Therefore AC = 10 cm and AE = 15cm and CE = (15-10) = 5 cm