Question

Could someone help me out?

Answer 1

Answers:

• DE = 1.1
• DF = 1.6
• BC = 4.8

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Explanation:

I recommend drawing the two triangles as shown below. The diagram isn't to scale, but all that matters is that we get the general idea down.

Your teacher gave you this info:

• angle A = angle E (red angles)
• angle C = angle F (blue angles)

These two pieces of info are enough to prove that triangle ABC is similar to triangle EDF. Use the angle angle (AA) similarity theorem to do this proof. The order of the lettering matters because it helps us see how the letters pair up.

• A and E go first
• B and D in the middle
• C and F go last

Since the triangles are similar, the scale factor to go from ABC to EDF is EF/AC = 2/6 = 1/3

In other words, the side lengths of triangle EDF are exactly 1/3 that of the corresponding lengths of ABC. Or we can reverse things to say the sides of ABC are 3 times longer than the sides of EDF.

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Use this scale factor to help determine the missing length ED.

(ED)/(AB) = scale factor

(ED)/(AB) = 1/3

(ED)/(3.3) = 1/3

ED = (1/3)*(3.3)

ED = 1.1

Note how ED/AB = (1.1)/(3.3) = 11/33 = 1/3

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While we don't know how long sides BC or DF are, we are told that DF is 3.2 units shorter compared to BC.

This means

DF = BC - 3.2

DF = x - 3.2

Then we can say,

(DF)/(BC) = scale factor

(x-3.2)/(x) = 1/3

3(x - 3.2) = x*1

3x - 9.6 = x

3x - x = 9.6

2x = 9.6

x = (9.6)/2

x = 4.8

So BC is x = 4.8 units long and DF is x-3.2 = 4.8-3.2 = 1.6 units long